Cellulose acylate film and method for producing same, and retardation film, polarizer and liquid crystal display device comprising the film

ABSTRACT

A cellulous acylate film in which X-ray diffractive intensity satisfies the following Formulae (I) to (V) and in which a half-value width of the peak at 2θ 2  is 2.8° or less as observed in the sectional view in a direction parallel to the transport direction of the film: 
       0.00≦ Ic   i   /Ic   o &lt;0.60;  Formula (I) 
         Iam=I   1 +{( I   3   −I   1 )/(2θ 3 −2θ 1 )}×(2θ 2 −2θ 1 );  Formula (II) 
         Ic=I   2   −Iam;   Formula (III) 
         Ic   i   =Ic   11   /Ic   12 ; and  Formula (IV) 
         Ic   o ={( Ic   21   /Ic   22 )+( Ic   31   /Ic   32 )}/2.  Formula (V)

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to a cellulose acylate film having opticalanisotropy and capable of being directly stuck to a polarizing film, anda method for producing thereof, and to a retardation film, a polarizer,and a liquid crystal device using the cellulose acylate film.

2. Background Art

A polymer film of typically cellulose ester, polyester, polycarbonate,cyclo-olefin polymer, vinyl polymer or polyimide is used in silverhalide photographic materials, retardation films, polarizers and imagedisplay devices. Films that are more excellent in point of the surfacesmoothness and the uniformity can be produced from these polymers, andthe polymers are therefore widely employed for optical films.

Of those, cellulose ester films having suitable moisture permeabilitycan be directly stuck to most popular polarizing films formed ofpolyvinyl alcohol (PVA)/iodine in on-line operation. Accordingly,cellulose acylate, especially cellulose acetate is widely employed as aprotective film for polarizers.

On the other hand, when cellulose acylate film is applied to opticaluse, for example, in retardation films, supports for retardation films,protective films for polarizers and liquid crystal display devices, thecontrol of their optical anisotropy is an extremely important element indetermining the performance (e.g., visibility) of display devices. Withthe recent demand for broadening the viewing angle of liquid crystaldisplay devices, improvement of retardation compensation in the devicesis desired, for which it is desired to suitably control the in-planeretardation Re (this may be simply referred to as Re) and thethickness-direction retardation Rth (this may be simply referred to asRth) of the retardation film to be disposed between a polarizing filmand a liquid crystal cell. In addition, it is desired to controlproperly not only optical characteristics of the film but also physicalcharacteristics of the film.

As a method of manufacturing the film having these optical properties,for example, methods of extending the film in a longitudinal directionor a transverse direction (see JP-A-2002-127244 and JP-A-2004-243628),sequentially extending the film in two axes (see JP-A-2005-330411),simultaneously extending the film in two axes (see JP-A-2005-22087), andextending the film in a thickness direction thereof (see JP-A-5-157911and JP-A-2000-231016) are disclosed. However, in the film manufacturedby these methods, there are problems that a balance control between Reand Rth is not enough and both of the optical property and the dynamicproperty of matter of the film are not improved.

SUMMARY OF THE INVENTION

An object of the invention is to provide a cellulous acylate film inwhich both of the optical property and the dynamic property of matterare improved and a method of manufacturing the same. In addition,another object of the invention is to provide a cellulous acylate filmand a method of manufacturing the same which have larger Re, positiveRth, and a property controlling a balance of Re and Rth. Further,another object of the invention is to provide a retardation film usingthe cellulous acylate film according to the invention and a polarizingplate having an excellent optical property by directly adhering thecellulous acylate film according to the invention, which serves as aretardation film, a supporter of the retardation film, or a protectivefilm of the polarizing plate, to a polarizing film. Further, the otherobject of the invention is to provide a liquid crystal display devicehaving high reliability.

The above-mentioned problem can be solved by the following means.

(1) A cellulous acylate film in which X-ray diffractive intensitysatisfies the following Formulae (I) to (V) and in which a half-valuewidth of the peak at 2θ₂ is 2.8° or less as observed in the sectionalview in a direction parallel to the transport direction of the film.

0.00≦Ic _(i) /Ic _(o<0.60;)  Formula (I)

Iam=I ₁+{(I ₃ −I ₁)/(2θ₃−2θ₁)}×(2θ₂−2θ₁);  Formula (II)

Ic=I ₂ −Iam;  Formula (III)

Ic _(i) =Ic ₁₁ /Ic ₁₂;  Formula (IV) and

Ic _(o)={(Ic ₂₁ /Ic ₂₂)+(Ic ₃₁ /Ic ₃₂)}/2.  Formula (V)

wherein when it is assumed that θ is the Bragg angle, 2θ₁ indicates 2θat which the intensity becomes the minimum in the 2θ range of 4° to 5°,2θ₂ indicates 2θ at which the intensity becomes the maximum in the 2θrange of 5° to 10°, 2θ₃ indicates 2θ at which the intensity becomes theminimum in the 2θ range of 14° to 16°, I₁ indicates a diffractiveintensity at 2θ₁, I₂ indicates a diffractive intensity at 2θ₂, I₃indicates a diffractive intensity at 2θ₃, Ic₁₁ and Ic₁₂ indicate Ic in adirection in which I₂ becomes the maximum as observed in a directionperpendicular to the surface of the film and Ic in a directionperpendicular thereto respectively, Ic₂₁ and Ic₂₂ indicate Ic in adirection in which I₂ becomes the maximum as observed in the sectionalview in a direction parallel to the transport direction of the film andIc in a direction perpendicular thereto respectively, and Ic₃₁, and Ic₃₂indicate Ic in a direction in which I₂ becomes the maximum as observedin the sectional view in a direction perpendicular to the transportdirection of the film and Ic in a direction perpendicular theretorespectively.(1-1) The cellulous acylate film according to (1), wherein thediffractive picture observed in the sectional view in a directionparallel to the transport direction of the film has at least one peak inthe 2θ range between 2θ₂ and 2θ₃, the maximum peak in the 2θ rangebetween 2θ₂ and 2θ₃ exists at 2θ₄ in the 2θ range of 10° to 12.5°, and ahalf-value width of the peak at 2θ₄ is less than 2°.(1-2) The cellulous acylate film according to (1), wherein thediffractive picture observed in the sectional view in a directionperpendicular to the transport direction of the film has at least onepeak in the 2θ range between 2θ₂ and 2θ₃, the maximum peak in the 2θrange between 2θ₂ and 2θ₃ exists at 204 in the 2θ range of 10° to 12.5°,and a half-value width of the peak at 2θ₄ is less than 2°.(2) The cellulous acylate film according to any one of (1) to (1-2),wherein the X-ray diffractive intensity observed in the sectional viewin a direction parallel to the transport direction of the film satisfiesthe following Formula (VI):

0.40≦Ic/(Iam+Ic)≦0.85.  Formula (VI)

(2-1) The cellulous acylate film according to any one of (1) to (2),wherein the X-ray diffractive intensity satisfies the following Formula(VII):

(Ic ₁₁ /Ic ₁₂)/(Ic ₃₁ /Ic ₃₂)<0.70.  Formula (VII)

(2-2) The cellulous acylate film according to any one of (1) to (2-1),wherein the X-ray diffractive intensity satisfies all of the followingFormulae (VIII) to (x):

Ic ₁₁ /Ic ₁₂)>50;  Formula (VIII)

Ic ₂₁ /Ic ₂₂)>170; and  Formula (IX)

Ic ₃₁ /Ic ₃₂)>100.  Formula (X)

(2-3) The cellulous acylate film according to any one of (1) to (2-2),wherein an angle formed by the direction of obtained Ic₁ and a directionin which a sound-wave propagation velocity becomes the maximum is in therange of 75° to 105°.(3) The cellulous acylate film according to any one of (1) to (2-3),wherein the haze is 3% or less.(4) The cellulous acylate film according to any one of (1) to (3),wherein the in-plane retardation is in the range of 5 to 600 nm and theretardation in the thickness direction is more than 0 nm.(5) The cellulous acylate film according to any one of (1) to (4),wherein an angle formed by a direction of an in-plane slow-phase axisand a direction in which a sound-wave propagation velocity becomes themaximum is in the range of 75° to 105°.(5-1) The cellulous acylate film according to any one of (1) to (5),wherein a fluctuation angle of direction of a slow-phase axis is lessthan 5°.(5-2) The cellulous acylate film according to any one of (1) to (5-1),wherein the cellulous acylate film has a monolayer structure.(6) A method of manufacturing a cellulous acylate film, the methodcomprising:

extending a cellulous acylate web by 15% to 300% by mass in a transportdirection in the state where an amount of a residual solvent is in therange of 5% to 1000% by mass; and

performing a heat treatment at the temperature of (−285×S+1000)° C. ormore and less than the melting point of a cellulous acylate film for0.01 minute or more and less than 60 minutes, wherein the step ofperforming the heat treatment includes contracting the film in the widthdirection of the film and S indicates a total substitution degree of thecellulous acylate film.

(6-1) A method of manufacturing a cellulous acylate film, the methodcomprising:

extending a cellulous acylate web by 15% to 300% in a transportdirection in the state where an amount of a residual solvent is in therange of 5% to 1000% by mass; and

performing a heat treatment at the temperature of Tc or more and lessthan the melting point of a cellulous acylate film for 0.01 minute ormore and less than 60 minutes, wherein the step of performing the heattreatment includes contracting the film in the width direction of thefilm, Tc indicates a crystallization temperature (unit: ° C.) of thecellulose acylate film before the heat treatment and S indicates a totalsubstitution degree of the cellulous acylate film.

(7) The method of manufacturing a cellulous acylate film according to(6) or (6-1), wherein the cellulous acylate web extends under thecondition that the temperature of the web is in the range of (Ts−100) to(Ts−0.1)° C. and Ts indicates a surface temperature of a flexiblesupporter.(7-1) The method of manufacturing a cellulous acylate film according toany one of (6) to (7), wherein a contraction ratio of the film in theheat treatment step of contracting the film in the width direction is inthe range of 5% to 80%.(7-2) The method of manufacturing a cellulous acylate film according toany one of (6) to (7-1), wherein an angle formed by a direction ofin-plane slow-phase axis of the film and a transport direction is in therange of 80° to 100°.(8) A cellulous acylate film manufactured by the method according to anyone of (6) to (7-2).(9) The cellulous acylate film according to any one of (1) to (5-2) and(8), wherein an angle formed by a direction of in-plane slow-phase axisof the film and a transport direction is in the range of 80° to 100°.(10) A retardation film having at least one sheet of cellulous acylatefilm according to any one of (1) to (5-2), (8), and (9).(11) A polarizing plate having at least one sheet of cellulous acylatefilm according to any one of (1) to (5-2), (8), and (9).(12) The polarizing plate according to (11), wherein the cellulousacylate film is directly adhered to a polarizing film.(13) A liquid crystal display device having at least one sheet of thecellulous acylate film according to any one of (1) to (5-2), (8), and(9), the retardation film according to (10), and the polarizing filmaccording to (11) or (12).

According to the invention, since the cellulous acylate film whichimproves both of the optical property and the dynamic property of matterand the method of manufacturing the same are provided, it is possible toprovide the excellent retardation film. In addition, it is possible toprovide the cellulous acylate film having larger Re, positive Rth, andthe property controlling the balance of Re and Rth and the method ofmanufacturing the same. The cellulous acylate film of the inventionhaving this retardation may be used as the retardation film itself andthe retardation film having large Re and Rth by adhering anotherretardation film. Further, since the cellulous acylate film according tothe invention has proper moisture permeability, the film may be adheredto the polarizing film on line. Accordingly, the polarizing plate havingexcellent visibility and high productivity may be provided. In addition,the liquid crystal display device having high reliability may beprovided.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating diffractive intensity in a direction inwhich I₂ becomes the maximum in the sectional view in a directionparallel to a transport direction of a film.

FIG. 2 is a diagram illustrating diffractive intensity in a directionperpendicular to a direction in which I₂ becomes the maximum in thesectional view in a direction parallel to a transport direction of afilm.

BEST MODE FOR CARRYING OUT THE INVENTION

Described in detail hereinafter are the cellulose acylate film and themethod for producing it, the retardation film, the polarizer and theliquid crystal display device of the invention. The constituent featuresmay be described below on the basis of representative embodiments of theinvention, but the invention is not limited to such embodiments. Thenumerical range represented by “-” herein means a range including thenumerical values described before and after “-” as the lowermost valueand the uppermost value, respectively.

<Cellulous Acylate Film>

In a cellulous acylate film according to the invention, X-raydiffractive intensity satisfies the Formula (I) below and a half-valuewidth of the peak at 2θ₂ is 2.8° or less as observed in the sectionalview in a direction parallel to the transport direction of the film.

By appropriately controlling the X-ray diffractive intensity, thecellulous acylate film of the invention can improve both of the opticalproperty and the dynamic property of matter.

0.00≦Ic _(i) /Ic _(o)<0.60;  Formula (I)

wherein Ic_(i) and Ic_(o) are represented by the following Formula (IV)and (V) respectively:

Ic _(i) =Ic ₁₁ /Ic ₁₂;  Formula (IV)

Ic _(o)={(Ic ₂₁ /Ic ₂₂)+(Ic ₃₁ /Ic ₃₂)}/2;  Formula (V)

wherein Ic₁₁ to Ic₃₂ are obtained by the Formulae (II) and (III) below,Ic₁₁ and Ic₁₂ indicate Ic in a direction in which I₂ becomes the maximumin a diffraction picture observed in a direction perpendicular to thesurface of the film and Ic in a direction perpendicular theretorespectively, Ic₂₁ and Ic₂₂ indicate Ic in a direction in which I₂becomes the maximum in a diffraction picture observed in the sectionalview in a direction parallel to the transport direction of the film andIc in a direction perpendicular thereto respectively, and Ic₃₁ and Ic₃₂indicate Ic in a direction in which I₂ becomes the maximum in adiffraction picture observed in the sectional view in a directionperpendicular to the transport direction of the film and Ic in adirection perpendicular thereto respectively:

Iam=I ₁+{(I ₃ −I ₁)/(2θ₃−2θ₁)}×(2θ₂−2θ₁);  Formula (II)

Ic=I ₂ −Iam;  Formula (III)

wherein when it is assumed that θ is the Bragg angle, 2θ₁ indicates 2θat which the intensity becomes the minimum in the 2θ range of 4° to 5°,2θ₂ indicates 2θ at which the intensity becomes the maximum in the 2θrange of 5° to 10°, 2θ₃ indicates 2θ at which the intensity becomes theminimum in the 2θ range of 14° to 16°, I₁ indicates a diffractiveintensity at 2θ₁, I₂ indicates a diffractive intensity at 2θ₂, I₃indicates a diffractive intensity at 2θ₃.

The observation in the sectional view in a direction parallel to thetransport direction means observation in a transverse direction as thefilm is cut in the transport direction.

[X-ray Diffractive Intensity]

According to the invention, the X-ray diffractive intensity of thecellulous acylate film was obtained (Cu Kα ray 50 kV 200 mA) from adiffraction picture of a beam transmitted in a direction perpendicularto the surface of the film by adjusting humidity of the film at 25° C.at relative humidity of 60% for 24 hours and then using an automaticX-ray diffracting device (RINT 2000: manufactured by RigakuCorporation.) and a general-purpose imaging-plate reading device (R-AXISDS3C/3 CL). Diffraction profiles were evaluated in the whole directionfrom the obtained diffraction picture. Iam and Ic were evaluated fromthe diffraction profiles in a direction in which peak intensity becomesthe maximum in the 2θ range of 5° to 10° in accordance with Formulas(II) and (III). Ic_(i) was evaluated from Ic₁₁ and Ic₁₂ obtained whenthe Ic is set as Ic₁₁ and the Ic is set as Ic₁₂ in a directionperpendicular to Ic₁₁ in accordance with Formula (IV). But, a part wherea beam is removed by a beam stopper is not interpreted when the 2θ₁ isevaluated. In the invention, peak positions are expressed by 2θ at thetop (maximum) of the peak.

A sample was manufactured by laminating thirty sheets of films which iscut by 10 mm×1 mm so that the transport direction of the film is in alongitudinal direction. By using the sample, a diffraction picture wastaken in the section view in a direction parallel to the transportdirection of the film in accordance with the above-described method. Icwas defined as Ic₂₁ in a direction when I₂ becomes the maximum inaccordance with the above-described method and Ic was defined as Ic₂₂ ina direction perpendicular thereto. Similarly, the sample which is cut by10 mm×1 mm so that a direction perpendicular to the transport directionof the film is in a longitudinal direction was determined to evaluateIc₃₁ and Ic₃₂. Ic_(o) was evaluated from the obtained Ic₂₁, Ic₂₂, Ic₃₁,and Ic₃₂ in accordance with Formula (V).

The cellulous acylate film of the invention is characterized in that theIc_(i) and Ic_(o) satisfy Formula (I). It is preferable thatIc_(i)/Ic_(o) is small. In order to achieve large Rth and positive Rth,it is preferable that the Ic_(i)/Ic_(o) is less than 0.60.

0.00≦Ic _(i) /Ic _(o)≦0.60.  Formula (I)

In the cellulous acylate film of the invention, it is more preferablethat the Ic_(i) and Ic_(o) satisfy the following Formula (Ia):

0.10≦Ic _(i) /Ic _(o)≦0.55.  Formula (Ia)

In the cellulous acylate film of the invention, it is further morepreferable that the Ic_(i) and Ic_(o) satisfy the following Formula(Ib):

0.20≦Ic _(i) /Ic _(o)≦0.50.  Formula (Ib)

In the cellulous acylate film of the invention, a half-value width ofthe peak at 2θ₂ observed in the sectional view in a direction parallelto the transport direction of the film is 2.8° or less, preferably inthe range of 0.5° to 2.5°, and more preferably in the range of 0.7° to2°.

The cellulose acylate film of the invention preferably has at least onepeak in the 2θ range between 2θ₂ and 2θ₃ in a diffraction pictureobserved in the sectional view in a direction parallel to the transportdirection of the film. The maximum peak in the 2θ range between 2θ₂ and2θ₃ exists in the 2θ range of 10° to 12.5° (2θ₄) and a half-value widthof the peak at 2θ₄ is less than 2°. The peak at 2θ₄ is not generallydetected in conventional cellulose acylate films and therefore theycannot attain desired optical properties. In these conventional films, ahalf-value width of the peak at 2θ₄ cannot be defined. The celluloseacylate film of the invention shows more desired optical properties whenit is controlled to have a peak at 2θ₄ between 10° and 12.5° and ahalf-value width of the peak at 2θ₄ of less than 2°.

In the cellulose acylate film of the invention, there preferably existtwo peaks between 2θ₂ and 2θ₃. The half-value width of the peak at 2θ₄is preferably in the range of 0.5°to 1.8°, more preferably in the rangeof 0.7° to 1.5°.

When there exist two peaks between 2θ₂ and 2θ₃ and one is at 2θ₄ and theother is at 2θ₅, the peak at 2θ₅ is preferably in the 2θ range of 12.5°to 14°.

The cellulose acylate film of the invention preferably has at least onepeak in the 2θ range between 2θ₂ and 2θ₃ in a diffraction pictureobserved in the sectional view in a direction perpendicular to thetransport direction of the film. The maximum peak in the 2θ rangebetween 2θ₂ and 2θ₃ exists in the 2θ range of 10° to 12.5° (2θ₄) and ahalf-value width of the peak at 2θ₄ is less than 2°.

In the cellulose acylate film of the invention, there preferably existtwo peaks between 2θ₂ and 2θ₃. The half-value width of the peak at 2θ₄is preferably in the range of 0.5° to 1.8°, more preferably in the rangeof 0.7° to 1.5°.

When there exist two peaks between 2θ₂ and 2θ₃ and one is at 2θ₄ and theother is at 2θ₅, the peak at 2θ₅ is preferably in the 2θ range of 12.5°to 14°.

In the cellulous acylate film according to the invention, it ispreferable that the Iam and Ic evaluated as observed in the sectionalview in a direction parallel to the transport direction of the filmsatisfy the following Formula (VI). By allowing Ic/(Iam+Ic) to be in0.40 or more, the directional property of the optical property and thedynamic property of matter may be preferable. By allowing Ic/(Iam+Ic) tobe in 0.85 or less, it may be difficult that the film weakens.

0.40≦Ic/(Iam+Ic)≦0.85.  Formula (VI)

In the cellulous acylate film according to the invention, it is morepreferable that the Iam and Ic evaluated as observed in the sectionalview in a direction perpendicular to the surface of the film of the filmsatisfy the following Formula (VIa):

0.45≦Ic/(Iam+Ic)≦0.80.  Formula (VIa)

It is further more preferable that Formula (VI) satisfies the followingFormula (VIb):

0.50≦Ic/(Iam+Ic)≦0.75.  Formula (VIb)

In the cellulous acylate film of the invention, it is preferable thatthe Ic₂₁, Ic₂₂, Ic₃₁, and Ic₃₂ satisfy the following Formula (VII):

(Ic ₂₁ /Ic ₂₂)/(Ic ₃₁ /Ic ₃₂)<0.70.  Formula (VII)

It is more preferable that the Ic₂₁, Ic₂₂, Ic₃₁, and Ic₃₂ satisfy thefollowing Formula (VIIa):

0.10≦(Ic ₂₁ /Ic ₂₂)/(Ic ₃₁ /Ic ₃₂)<0.60.  Formula (VIIa)

It is further more preferable that the Ic₂₁, Ic₂₂, Ic₃₁, and Ic₃₂satisfy the following Formula (VIIb):

0.20≦(Ic ₂₁ /Ic ₂₂)/(Ic ₃₁ /Ic ₃₂)≦0.55.  Formula (VIIb)

In the cellulous acylate film of the invention, it is preferable thatthe Ic₁₁, Ic₁₂, Ic₂₁, Ic₂₂, Ic₃₁, and Ic₃₂ satisfy the followingFormulas (VIII) to (X):

Ic ₁₁ /Ic ₁₂>50;  Formula (VIII)

Ic ₂₁ /Ic ₂₂>170; and  Formula (IX)

Ic ₃₁ /Ic ₃₂>100.  Formula (X)

It is more preferable that the Ic₁₁, Ic₁₂, Ic₂₁, Ic₂₂, Ic₃₁, and Ic₃₂satisfy the following Formulas (VIIIa) to (Xa):

80<Ic ₁₁ /Ic ₁₂<10000;  Formula (VIIIa)

200<Ic ₂₁ /Ic ₂₂<10000; and  Formula (IXa)

130<Ic ₃₁ /Ic ₃₂<10000.  Formula (Xa)

It is further more preferable that the Ic₁₁, Ic₁₂, Ic₂₁, Ic₂₂, Ic₃₁, andIc₃₂ satisfy the following Formulas (VIIIb) to (Xb):

110<Ic ₁₁ /Ic ₁₂<1000;  Formula (VIIIb)

230<Ic ₂₁ /Ic ₂₂<1000; and  Formula (IXb)

160<Ic ₃₁ /Ic ₃₂<1000.  Formula (Xb)

[Haze]

According to the invention, the haze of the cellulous acylate film wasmeasured by adjusting the humidity of the film at 25° at relativehumidity of 60% for 24 hours and then using a haze-meter (NDH 2000:manufactured by NIPPON DENSHOKU KOGYO KABUSHIKI KAISHA).

In general, a haze value of a polymer film increases depending on theincrease in X-ray diffractive intensity. However, it is preferable thatthe haze value is low in the film used for an optical film such as aliquid crystal display device like the invention. The circumstance canbe realized in the way to appropriately adjust the peaks at 2θ₂ and 2θ₄in the above-described X-ray diffraction profiles. It is preferable thatthe haze of the cellulous acylate film according to the invention is 3%or less, more preferable in the range of 0.0% to 2.0%, further morepreferable in the range of 0.1% to 1.0%, and the most preferable in therange of 0.1% to 0.5%.

[Sound-Wave Propagation Velocity (Acoustic Velocity)]

In order to achieve the cellulous acylate film of the inventionimproving both of the optical property and the dynamic property ofmatter, as described below, it is preferable to control a direction ofan in-plane slow phase axis and a direction in which the sound-wavepropagation velocity (hereinafter, referred to as “sound velocity”)becomes the maximum.

The direction in which the sound-wave propagation velocity becomes themaximum was evaluated, as a direction in which a propagation velocity ofa longitudinal-wave vibrations of ultrasonic pulse becomes the maximum,by adjusting humidity of the film at 25° C. at relative humidity of 60%for 24 hours and then using an alignment-property meter (SST-2500:manufactured by Nomura Shoji Co., Ltd.).

[Retardation]

The retardation in the invention is described. In this description, Reand Rth (unit: nm) are obtained according to the following method. Afilm to be analyzed is conditioned at 25° C. and a relative humidity of60% for 24 hours. Using a prism coupler (Model 2010 Prism Coupler, byMetricon) and using a solid laser at 532 nm, the mean refractivity (n)of the film, which is represented by the following formula (a), isobtained at 25° C. and a relative humidity of 60%.

n=(n _(TE)×2+n _(TM))/3  (a)

wherein n_(TE) is the refractive index measured with polarizing light inthe in-plane direction of the film; and n_(TM) is the refractive indexmeasured with polarizing light in the normal direction to the face ofthe film.

Re(λ) and Rth(λ) represent, herein, the retardation in the plane and theretardation in the thickness direction, respectively, at a wavelength ofλ. Re(λ) is measured with KOBRA21ADH or WR (by Oji ScientificInstruments) while allowing light having the wavelength of λ nm to enterin the normal direction of a film.

In case where the film to be measured is a film that is represented by auniaxial or biaxial indicatrix, Rth(λ) is computed by the followingmethod.

That is, respective Re(λ)s are measured at total eleven points in thenormal direction of the film relative to the film surface and indirections inclined every 10° up to 50° on one side from the normal linearound an in-plane slow axis (determined by KOBURA 21AD or WR) as aninclination axis (rotation axis) (in case where no slow axis exists, anydirection in the plane of the film is defined as a rotation axis) for anincoming light of a wavelength of λ nm, and KOBRA 21ADH or WR computesthe Rth(λ) on the basis of the measured retardation, an assumed value ofan average refraction index and an input thickness.

In the above instance, when the retardations are expressed as Re and Rthwithout referring to specific λ, they are the values measured by use ofthe light in the wavelength of 590 nm. In case where a film has adirection in which the retardation becomes zero at a certain inclinationangle from the normal line relative to the film surface around thein-plane slow axis direction (rotation axis), the retardation at aninclination angle greater than the inclination angle is computed byKOBRA 21ADH or WR after changing the sign thereof to negative.

Further, it is also possible to compute Rth according to the followingformulae (b) and (c) by measuring the retardation in two arbitrarilyinclined directions around the slow axis as the inclination axis(rotation axis) (in case where no slow axis exists, any direction in theplane of the film is defined as a rotation axis), and basing on themeasured value, an assumed value on an average refraction index and aninput thickness value.

$\begin{matrix}{{{Re}(\theta)} = {\quad{\left\lbrack {{nx} - \frac{{ny} \times {nz}}{\sqrt{\left( {{ny}\; {\sin \left( {\sin^{- 1}\left( \frac{\sin \left( {- \theta} \right)}{nx} \right)} \right)}} \right)^{2} + \left( {{nz}\; {\cos \left( {\sin^{- 1}\left( \frac{\sin \left( {- \theta} \right)}{nx} \right)} \right)}} \right)^{2}}}} \right\rbrack \times \frac{d}{\cos \left( {\sin^{- 1}\left( \frac{\sin \left( {- \theta} \right)}{nx} \right)} \right)}}}} & (b)\end{matrix}$

Note:

The above Re (θ) represents the retardation in a direction that inclinesin the degree of θ from the normal direction. In the formula (b), nxrepresents the refraction index in the slow axis direction in the plane,ny represents the refraction index in the direction perpendicular to nxin the plane, and nz represents the refraction index in the directionperpendicular to the directions of nx and ny.

Rth=((nx+ny)/2−nz)×d  (c)

In case where the film to be measured is a film that can not beexpressed by a uniaxial or biaxial indicatrix, that is, a so-called filmhaving no optic axis, Rth(λ) is computed according to the followingmethod.

Rth(λ) is computed from the retardation that is obtained by measuringthe Re(λ) at total eleven points in directions inclined every 10° from−50° up to +50° from the normal line relative to the film surface aroundan in-plane slow axis (determined by KOBURA 21AD or WR) as aninclination axis (rotation axis) for an incoming light of a wavelengthof λ nm entering from each of the directions of inclination, an assumedvalue of an average refraction index and input thickness with KOBRA21ADH or WR.

By inputting the value of these average refraction indices andthickness, KOBRA 21ADH or WR computes nx, ny, nz. From the computed nx,ny, nz, Nz=(nx−nz)/(nx−ny) is computed further.

In the retardation value of the cellulous acylate film according to theinvention, it is preferable that the in-plane retardation (Re) is in therange of 5 to 600 nm, more preferably in the range of 30 to 600 nm,further more preferably in the range of 50 to 400 nm, and the mostpreferably in the range of 100 to 300 nm. It is preferable that theretardation (Rth) in the film-thickness direction is more than 0 nm,more preferably in the range of 10 to 600 nm, and further morepreferably in the range of 20 to 200 nm.

In addition, it is preferable that the retardations satisfy thefollowing both Formulas (A) and (B):

|Rth|/Re≦1.0; and  Formula (A)

5≦Re≦600.  Formula (B)

wherein Re indicates a retardation value (unit: nm) in the in-planedirection of the cellulous acylate film and Rth indicates a retardationvalue (unit: nm) in the film-thickness direction of the cellulousacylate film.

It is preferable that the cellulous acylate film of the inventionfurther satisfies the following Formulas (Aa) and (Ba):

|Rth|/Re≦0.5; and  Formula (Aa)

30≦Re≦600.  Formula (Ba)

It is more preferable that the cellulous acylate film of the inventionsatisfies the following Formulas (Ab) and (Bb):

|Rth|/Re≦0.4; and  Formula (Ab)

50≦Re≦400.  Formula (Bb)

It is the most preferable that the cellulous acylate film of theinvention satisfies the following Formulas (Ac) and (Bc):

|Rth|/Re≦0.3; and  Formula (Ac)

100≦Re≦300.  Formula (Bc)

In the cellulous acylate film of the invention, it is preferable that anangle formed by a direction of the in-plane slow phase axis and adirection in which the sound-wave propagation velocity becomes themaximum is in the range of 75° to 105°, more preferably in the range of85° to 95°, further more preferably in the range of 87° to 93°, and themost preferably in the range of 89° to 91°. In the method ofmanufacturing the cellulous acylate film of the invention, it ispreferable that an angle formed by a direction of the in-planeslow-phase axis of the film and the transport direction is in the rangeof 85° to 95°, more preferably in the range of 87° to 93°, further morepreferably in the range of 89° to 91°, and the most preferably in therange of 89.5° to 90.5°.

[Thickness]

The thickness of the cellulose acylate film of the invention ispreferably 20 μm-180 μm, more preferably 40 μm-160 μm, even morepreferably 60 μm-140 μm. When the thickness is less than 20 μm, thehandling ability upon processing the film for a polarizer, or the curingof the polarizer is undesirable. The thickness unevenness of thecellulose acylate film of the invention is preferably 0-2%, morepreferably 0-1.5%, especially preferably 0-1%, in both of the transferdirection and the width direction.

[Moisture Permeability]

Next, moisture permeability is described. The moisture permeability inthe invention means an evaluated value from the mass change (g/(m²·day))before and after humidity conditioning when respective films are usedfor capping and sealing cups containing calcium chloride to be leftunder conditions of 40° C. and a relative humidity of 90% for 24 hours.

The moisture permeability rises with the rise of temperature, and alsowith the rise of humidity, but the relation between the magnitudes ofthe moisture permeability of films is changeless independently ofrespective conditions. Therefore, in the invention, the value of masschange at 40° C. and a relative humidity of 90% is employed as thestandard.

The moisture permeability of the cellulose acylate film of the inventionis preferably 100-400 g/(m²·day). The use of a film having the moisturepermeability of 100-400 g/(m²·day) allows the film to be stuck directlyto a polarizing film. The moisture permeability is preferably 100-350g/(m²·day), more preferably 150-300 g/(m²·day).

[Cellulose Acylate]

Examples of the polymer which is the constitutive element of thecellulose acylate film of the invention include a cellulose acylatecompound, and a compound having acyl-substituted cellulose skeletonobtained by biologically or chemically introducing a functional groupinto a basic material, which is cellulose.

The polymer may be powdery or granular, or may be pelletized.

Preferably, the water content of the polymer is at most 1.0% by mass,more preferably at most 0.7% by mass, most preferably at most 0.5% bymass. As the case may be, the water content may be preferably at most0.2% by mass. In case where the water content of the polymer is outsidethe preferred range, then it is desirable that the polymer is dried byheating before use.

One or more such polymers may be used herein either singly or ascombined.

Cellulose acylate is preferably used for the main component polymer ofthe cellulose acylate film of the invention. The “main componentpolymer” as referred to herein is meant to indicate the polymer itselfwhen the film is formed of a single polymer, and when the film is formedof different polymers, then it indicates the polymer having the highestmass fraction of all the polymers constituting the film.

The cellulose acylate is an ester of cellulose with an carboxylic acid.The acid to constitute the ester is preferably a fatty acid having from2 to 22 carbon atoms, more preferably a lower fatty acid having from 2to 4 carbon atoms.

In the cellulose acylate, all or a part of the hydrogen atoms of thehydroxyl groups existing at the 2-, 3- and 6-positions of the glucoseunit constituting the cellulose are substituted with an acyl group.Examples of the acyl group are acetyl, propionyl, butyryl, isobutyryl,pivaloyl, heptanoyl, hexanoyl, octanoyl, decanoyl, dodecanoyl,tridecanoyl, tetradecanoyl, hexadecanoyl, octadecanoyl,cyclohexanecarbonyl, oleoyl, benzoyl, naphthylcarbonyl and cinnamoyl.The acyl group is preferably acetyl, propionyl, butyryl, dodecanoyl,octadecanoyl, pivaloyl, oleoyl, benzoyl, naphthylcarbonyl, cinnamoyl,most preferably acetyl, propionyl, butyryl.

The cellulose ester may be an ester of cellulose with differentcarboxylic acids. The cellulose acylate may be substituted withdifferent acyl groups.

For the cellulose acylate film of the invention, a substitution degreeof acyl is preferably 2.50 to 3.00 from the viewpoint of improvingexpression in Re, or reducing in the moisture permeability and the heattreatment temperature. It is more preferred that cellulose acylate hasthe substitution degree of acyl of 2.70 to 2.99, even more preferably2.80 to 2.98, most preferably 2.90 to 2.98.

Regarding a method for producing cellulose acylate, its basic principleis described in Wood Chemistry by Nobuhiko Migita et al., pp. 180-190(Kyoritsu Publishing, 1968). One typical method for producing celluloseacylate is a liquid-phase acylation method with carboxylic acidanhydride-carboxylic acid-sulfuric acid catalyst. Concretely, a startingmaterial for cellulose such as cotton linter or woody pulp is pretreatedwith a suitable amount of a carboxylic acid such as acetic acid, andthen put into a previously-cooled acylation mixture for esterificationto produce a complete cellulose acylate (in which the overallsubstitution degree of acyl group in the 2-, 3- and 6-positions isnearly 3.00). The acylation mixture generally includes a carboxylic acidserving as a solvent, a carboxylic acid anhydride serving as anesterifying agent, and sulfuric acid serving as a catalyst. In general,the amount of the carboxylic acid anhydride to be used in the process isstoichiometrically excessive over the overall amount of water existingin the cellulose that reacts with the anhydride and that in the system.

Next, after the acylation, the excessive carboxylic acid anhydride stillremaining in the system is hydrolyzed, for which, water orwater-containing acetic acid is added to the system. Then, for partiallyneutralizing the esterification catalyst, an aqueous solution thatcontains a neutralizing agent (e.g., carbonate, acetate, hydroxide oroxide of calcium, magnesium, iron, aluminium or zinc) may be addedthereto. Then, the resulting complete cellulose acylate is saponifiedand ripened by keeping it at 20 to 90° C. in the presence of a smallamount of an acylation catalyst (generally, sulfuric acid remaining inthe system), thereby converting it into a cellulose acylate having adesired substitution degree of acyl group and a desired polymerizationdegree. At the time when the desired cellulose acylate is obtained, thecatalyst still remaining in the system is completely neutralized withthe above-mentioned neutralizing agent; or the catalyst therein is notneutralized, and the cellulose acylate solution is put into water ordiluted acetic acid (or water or diluted acetic acid is put into thecellulose acylate solution) to thereby separate the cellulose acylate,and thereafter this is washed and stabilized to obtain the intendedproduct, cellulose acylate.

Preferably, the polymerization degree of the cellulose acylate is from150 to 500 as the viscosity-average polymerization degree thereof, morepreferably from 200 to 400, even more preferably from 220 to 350. Theviscosity-average polymerization degree may be measured according to alimiting viscosity method by Uda et al. (Kazuo Uda, Hideo Saito; Journalof the Fiber Society of Japan, Vol. 18, No. 1, pp. 105-120, 1962). Themethod for measuring the viscosity-average polymerization degree isdescribed also in JP-A-9-95538.

Cellulose acylate where the amount of low-molecular components is smallmay have a high mean molecular weight (high polymerization degree), butits viscosity may be lower than that of ordinary cellulose acylate. Suchcellulose acylate where the amount of low-molecular components is smallmay be obtained by removing low-molecular components from celluloseacylate produced in an ordinary method. The removal of low-molecularcomponents may be attained by washing cellulose acylate with a suitableorganic solvent. Cellulose acylate where the amount of low-molecularcomponents is small may be obtained by synthesizing it. In case wherecellulose acylate where the amount of low-molecular components is smallis synthesized, it is desirable that the amount of the sulfuric acidcatalyst in acylation is controlled to be from 0.5 to 25 parts by massrelative to 100 parts by mass of cellulose. When the amount of thesulfuric acid catalyst is controlled to fall within the range, thencellulose acylate having a preferable molecular weight distribution(uniform molecular weight distribution) can be produced.

The starting material, cotton for cellulose ester and methods forproducing it are described also in Hatsumei Kyokai Disclosure Bulletin(No. 2001-1745, issued Mar. 15, 2001, Hatsumei Kyokai), pp. 7-12.

[Production of Cellulose Acylate Film]

The cellulose acylate film of the invention may be produced from acellulose acylate solution that contains cellulose acylate and variousadditives, according to a method of solution casting film formation. Incase where the melting point of the cellulose acylate film of theinvention or the melting point of a mixture of the cellulose acylatewith various additives is lower than the decomposition temperaturethereof and is higher than the stretching temperature thereof, then thepolymer film may also be produced according to a method of melt filmformation. The melting point of the cellulose acylate film is measuredby the measuring method described later in an example of the invention.The cellulose acylate film of the invention may be produced according tosuch a method of melt film formation, and the method of melt filmformation is described in JP-A-2000-352620.

[Cellulose Acylate Solution] (Solvent)

The cellulose acylate film of the invention may be produced, forexample, according to a method of solution casting film formation wherea cellulose acylate solution that contains a polymer and optionallyvarious additives is cast into a film.

The main solvent of the cellulose acylate solution to be used inproducing the cellulose acylate film of the invention is preferably anorganic solvent that is a good solvent for the cellulose acylate. Theorganic solvent of the type is preferably one having a boiling point ofnot higher than 80° C. from the viewpoint of reducing the load indrying. More preferably, the organic solvent has a boiling point of from10 to 80° C., even more preferably from 20 to 60° C. As the case may be,an organic solvent having a boiling point of from 30 to 45° C. may alsobe preferably used for the main solvent.

The main solvent includes halogenohydrocarbons, esters, ketones, ethers,alcohols and hydrocarbons, which may have a branched structure or acyclic structure. The main solvent may have two or more functionalgroups of any of esters, ketones, ethers and alcohols (i.e., —O—, —CO—,—COO—, —OH). Further, the hydrogen atoms in the hydrocarbon part ofthese esters, ketones, ethers and alcohols may be substituted with ahalogen atom (especially, fluorine atom). Regarding the main solvent ofthe cellulose acylate solution to be used in producing the celluloseacylate film of the invention, when the solvent of the solution is asingle solvent, then it is the main solvent, but when the solvent is amixed solvent of different solvents, then the main solvent is thesolvent having the highest mass fraction of all the constitutivesolvents.

The halogenohydrocarbon is preferably a chlorohydrocarbon, includingdichloromethane and chloroform, and dichloromethane is more preferred.

The ester includes, for example, methyl formate, ethyl formate, methylacetate, ethyl acetate.

The ketone includes, for example, acetone, methyl ethyl ketone.

The ether includes, for example, diethyl ether, methyl tert-butyl ether,diisopropyl ether, dimethoxymethane, 1,3-dioxolan, 4-methyldioxolan,tetrahydrofuran, methyltetrahydrofuran, 1,4-dioxane.

The alcohol includes, for example, methanol, ethanol, 2-propanol.

The hydrocarbon includes, for example, n-pentane, cyclohexane, n-hexane,benzene, toluene.

The organic solvent that may be combined with the main solvent includeshalogenohydrocarbons, esters, ketones, ethers, alcohols andhydrocarbons, which may have a branched structure or a cyclic structure.The organic solvent may have two or more functional groups of any ofesters, ketones, ethers and alcohols (i.e., —O—, —CO—, —COO—, —OH).Further, the hydrogen atoms in the hydrocarbon part of these esters,ketones, ethers and alcohols may be substituted with a halogen atom(especially, fluorine atom).

The halogenohydrocarbon is preferably a chlorohydrocarbon, includingdichloromethane and chloroform, and dichloromethane is more preferred.

The ester includes, for example, methyl formate, ethyl formate, propylformate, pentyl formate, methyl acetate, ethyl acetate, pentyl acetate.

The ketone includes, for example, acetone, methyl ethyl ketone, diethylketone, diisobutyl ketone, cyclopentanone, cyclohexanone,methylcyclohexanone.

The ether includes, for example, diethyl ether, methyl tert-butyl ether,diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane,1,3-dioxolan, 4-methyldioxolan, tetrahydrofuran, methyltetrahydrofuran,anisole, phenetole.

The alcohol includes, for example, methanol, ethanol, 1-propanol,2-propanol, 1-butanol, 2-butanol, tert-butanol, 1-pentanol,2-methyl-2-butanol, cyclohexanol, 2-fluoroethanol,2,2,2-trifluoroethanol, 2,2,3,3-tetrafluoro-1-propanol.

The hydrocarbon includes, for example, n-pentane, cyclohexane, n-hexane,benzene, toluene, xylene.

The organic solvent having two or more different types of functionalgroups includes, for example, 2-ethoxyethyl acetate, 2-methoxyethanol,2-butoxyethanol, methyl acetacetate.

It is desirable that the total solvent for it contains from 5% to 30% bymass, more preferably from 7% to 25% by mass, even more preferably from10% to 20% by mass of alcohol from the viewpoint of reducing the loadfor film peeling from band.

Preferred examples of the combination of organic solvents for use as thesolvent in the cellulose acylate solution to be used in producing thecellulose acylate film of the invention are mentioned below, to which,however, the invention should not be limited. The numerical data forratio are parts by mass.

(1) Dichloromethane/methanol/ethanol/butanol=80/10/5/5 (2)Dichloromethane/methanol/ethanol/butanol=80/5/5/10

(3) Dichloromethane/isobutyl alcohol=90/10

(4) Dichloromethane/acetone/methanol/propanol=80/5/5/10 (5)Dichloromethane/methanol/butanol/cyclohexane=80/8/10/2

(6) Dichloromethane/methyl ethyl ketone/methanol/butanol=80/10/5/5

(7) Dichloromethane/butanol=90/10

(8) Dichloromethane/acetone/methyl ethylketone/ethanol/butanol=68/10/10/7/5

(9) Dichloromethane/cyclopentanone/methanol/pentanol=80/2/15/3

(10) Dichloromethane/methyl acetate/ethanol/butanol=70/12/15/3(11) Dichloromethane/methyl ethyl ketone/methanol/butanol=80/5/5/10(12) Dichloromethane/methyl ethylketone/acetone/methanol/pentanol=50/20/15/5/10(13) Dichloromethane/1,3-dioxolan/methanol/butanol=70/15/5/10

(14) Dichloromethane/dioxane/acetone/methanol/butanol=75/5/10/5/5

(15) Dichloromethane/acetone/cyclopentanone/ethanol/iso-butylalcohol/cyclohexanone=60/18/3/10/7/2(16) Dichloromethane/methyl ethyl ketone/acetone/isobutylalcohol=70/10/10/10(17) Dichloromethane/acetone/ethyl acetate/butanol/hexane=69/10/10/10/1(18) Dichloromethane/methyl acetate/methanol/isobutylalcohol=65/15/10/10

(19) Dichloromethane/cyclopentanone/ethanol/butanol=85/7/3/5 (20)Dichloromethane/methanol/butanol=83/15/2 (21) Dichloromethane=100 (22)Acetone/ethanol/butanol=80/15/5

(23) Methyl acetate/acetone/methanol/butanol=75/10/10/5(24) 1,3-dioxolan=100

(25) Dichloromethane/methanol=92/8 (26) Dichloromethane/methanol=90/10(27) Dichloromethane/methanol=87/13 (28) Dichloromethane/ethanol=90/10

A detailed description of a case where a non-halogen organic solvent isthe main solvent is given in Hatsumei Kyokai Disclosure Bulletin (No.2001-1745, issued Mar. 15, 2001, Hatsumei Kyokai), which may beconveniently referred to herein.

(Solution Concentration)

The polymer concentration in the cellulose acylate solution to beprepared herein is preferably from 5% to 40% by mass, more preferablyfrom 10% to 30% by mass, most preferably from 15% to 30% by mass.

The polymer concentration may be so controlled that it could be apredetermined concentration in the stage where polymer is dissolved insolvent. Apart from it, a solution having a low concentration (e.g.,from 4% to 14% by mass) is previously prepared, and then it may beconcentrated by evaporating the solvent from it. On the other hand, asolution having a high concentration is previously prepared, and it maybe diluted. The polymer concentration in the solution may also bereduced by adding additive thereto.

(Additive)

The cellulose acylate solution to be used for producing the celluloseacylate film of the invention may contain various liquid or solidadditives in accordance with the use of the film, in the steps ofproducing it. Examples of the additives are plasticizer (its preferredamount is from 0.01% to 10% by mass of the polymer—the same shall applyhereunder), UV absorbent (0.001% to 1% by mass), powdery particleshaving a mean particle size of from 5 to 3000 nm (0.001% to 1% by mass),fluorine-containing surfactant (0.001% to 1% by mass), release agent(0.0001% to 1% by mass), antioxidant (0.0001% to 1% by mass), opticalanisotropy-controlling agent (0.01% to 10% by mass), IR absorbent(0.001% to 1% by mass).

The plasticizer and the optical anisotropy-controlling agent arecompounds having both a hydrophobic part and a hydrophilic part. Thesecompounds are aligned between the polymer chains, thereby changing theretardations of the film. When the compounds are combined with celluloseacylate that is especially preferably used in the invention, thecompounds may improve the hydrophobicity of the film and may reduce thehumidity-dependent change of the retardation thereof. In addition, whenthe compounds are combined with the UV absorbent or IR absorbent, thecompounds may effectively control the wavelength dependence of theretardation of the polymer film. The additives to be used in thecellulose acylate film of the invention are preferably those notsubstantially evaporating in the step of drying the film.

From the viewpoint of reducing the humidity-dependent retardation changeof the film, the amount of these additives to be added to the film ispreferably larger, but with the increase in the amount to be added,there may occur some problems in that the glass transition temperatureof the polymer film may lower and the additives may evaporate awayduring the process of film production. Accordingly, in case wherecellulose acetate which is preferably used in the invention is used asthe polymer, then the amount of the plasticizer or the opticalanisotropy-controlling agent to be added is preferably in the range of0.01% to 30% by mass, more preferably in the range of 2% to 30% by mass,even more preferably in the range of 5% to 20% by mass relative to thepolymer.

For the plasticizer or the optical anisotropy-controlling agent whichcan be suitably used in case that cellulose acylate is used as a polymerwhich constitutes the cellulose acylate film, specifically, there can beexemplified a plasticizer described in JP-A-2005-104148 on pages 33 to34, and an optical anisotropy-controlling agent described inJP-A-2005-104148 on pages 38 to 89. For the IR absorbent, it isdescribed in JP-A-2001-194522 as an example. The time of adding theadditives may be properly determined depending on the types of theadditives. For the additives, it is described in Hatsumei KyokaiDisclosure Bulletin (No. 2001-1745, issued Mar. 15, 2001, HatsumeiKyokai) on pages 16 to 22.

(Preparation of Cellulose Acylate Solution)

The cellulose acylate solution may be prepared, for example, accordingto the methods described in JP-A-58-127737, JP-A-61-106628,JP-A-2-276830, JP-A-4-259511, JP-A-5-163301, JP-A-9-95544,JP-A-10-45950, JP-A-10-95854, JP-A-11-71463, JP-A-11-302388,JP-A-11-322946, JP-A-11-322947, JP-A-11-323017, JP-A-2000-53784,JP-A-2000-273184 and JP-A-2000-273239. Concretely, cellulose acylate andsolvent are mixed and stirred so that the cellulose acylate is swollen,and as the case may be, this is cooled or heated so as to dissolve thecellulose acylate, and thereafter this is filtered to obtain a celluloseacylate solution.

According to the invention, in order to improve solubility of celluloseacylate in a solvent, there is included a process of cooling and/orheating a mixture of cellulose acylate and a solvent.

In case of cooling the mixture of cellulose acylate and a solvent inwhich a halogen-containing organic solvent is used as the solvent, it ispreferred to include a process of cooling the mixture at −100 to 10° C.Further, it is preferred to include a process of swelling the mixture at−10 to 39° C. before the process of cooling, and a process of heatingthe mixture at 0 to 39° C. after the process of cooling.

In case of heating the mixture of cellulose acylate and a solvent inwhich a halogen-containing organic solvent is used as the solvent, it ispreferred to include a process of dissolving the cellulose acylate inthe solvent according to at least one of the following methods (a) and(b).

(a): A mixture is swollen at −10 to 39° C., and then heated at 0 to 39°C.

(b): A mixture is swollen at −10 to 39° C., and then heated at 40 to240° C. under pressure of 0.2 to 30 MPa. After that, the mixture iscooled at 0 to 39° C.

In addition, in case of cooling the mixture of cellulose acylate and asolvent in which a non-halogen-containing organic solvent is used as thesolvent, it is preferred to include a process of cooling the mixture at−100 to −10° C. Further, it is preferred to include a process ofswelling the mixture at −10 to 55° C. before the process of cooling, anda process of heating the mixture at 0 to 57° C. after the process ofcooling.

In case of heating the mixture of cellulose acylate and a solvent inwhich a non-halogen-containing organic solvent is used as the solvent,it is preferred to include a process of dissolving the cellulose acylatein the solvent according to at least one of the following methods (c)and (d).

(c): A mixture is swollen at −10 to 55° C., and then heated at 0 to 57°C.

(d): A mixture is swollen at −10 to 55° C., and then heated at 40 to240° C. under pressure of 0.2 to 30 MPa. After that, the mixture iscooled at 0 to 57° C.

[Casting, Drying]

The cellulose acylate film of the invention may be produced according toa conventional method of solution casting film formation, using aconventional apparatus for solution casting film formation. Concretely,a dope (polymer solution) prepared in a dissolver (tank) is filtered,and then once stored in a storage tank in which the dope is degassed tobe a final dope. The dope is kept at 30° C., and fed into a pressure diefrom the dope discharge port of the tank, via a metering pressure gearpump through which a predetermined amount of the dope can be fed withaccuracy, for example, based on the controlled revolution thereof, andthen the dope is uniformly cast onto the metal support of a casting unitthat runs endlessly, via the slit of the pressure die (casting step).Next, at a peeling point at which the metal support reaches almost afterhaving traveled round the drum, a semi-dried dope film (this may bereferred to as a web) is peeled from the metal support.

In a heat treatment of the cellulous acylate film of the invention, adynamic different force applied to the cellulous acylate film, that is,the control of an external force applied to the cellulous acylatepolymer in the state of the cellulous acylate web is important. Bycontrolling the different force, it is possible to control a growthdirection in the film-thickness direction of a structure, observed withthe X-ray diffraction, growing in the heat treatment process.Specifically, the cellulous acylate web extends by 15% to 300% in thetransport direction, preferably in the range of 18% to 200%, morepreferably in the range of 20% to 100%. By performing the extension inthese ranges, a balance between a structure observed with the X-raydiffraction growing in the in-plane direction and a structure observedwith the X-ray diffraction growing in the film-thickness directionmaintain more properly. The cellulous acylate film in which the balancebetween the large Re and the positive Rth of the film is controlled canbe manufactured.

The cellulous acylate web may extend by a circumferential velocitydifference between a metal supporter velocity and a peeling velocity(peeling roll draw).

At this time, the residual solvent amount of the cellulous acylate webis calculated on the basis of the following Formula and defined in therange of 5% to 1000% by mass. It is preferable that the residual solventamount is in the range of 30% to 500% by mass, more preferably in therange of 50% to 400% by mass, and further more preferably in the rangeof 100% to 300% by mass. When the web extends with the residual solventamount by 5% or less by mass, the haze increases. When the web extendswith the residual solvent amount by 1000% by mass, the external forceapplied to the polymer eases, thereby not obtaining sufficient effects.The concentration of the cellulous acylate solution, the temperature orvelocity of the metal supporter, the temperature or wind-force of a drywind, the solvent gas concentration in the dry atmosphere, and the likeare modified, thereby properly adjusting the residual solvent amount ofthe cellulous acylate web.

AMOUNT OF RESIDUAL SOLVENT (mass %)={(M−N)/N}×100 wherein M indicates amass of the cellulose acylate film before it is inserted into a heattreatment zone and N indicates a mass when the cellulous acylate film isallowed to be dry at 110° C. for 3 hours before it is inserted into theheat treatment zone.

In the process of extending the cellulous acylate web, it is preferablethat the temperature of the film surface of the web is low in the viewpoint of applying the external force to the cellulous acylate film. Itis preferable that the temperature of the web is in the range of(Ts−100) to (Ts−0.1)° C., more preferably in the range of (Ts−50) to(Ts−1)° C., and further more preferably in the range of (Ts−20) to(Ts−3)° C. Herein, Ts indicates a surface temperature of a flexiblesupporter. When the temperature of the flexible supporter is set to apartially different temperature, Ts indicates a surface temperature atthe center portion of the supporter.

As a result, the cellulous acylate web passing the extending process inthis manner is transported to the dry zone. Then, the drying process iscompleted while both ends of the web are gripped by tenter clips or theweb is transported to a roll group. In the invention, preferably, ametal belt or a metal drum may be used as the metal supporter.

Thus dried film has a residual solvent amount of preferably 0-2% bymass, more preferably 0-1% by mass. This film may be directlytransported to a stretching zone or heat treatment zone, or may be woundand then subjected to stretching or heat treatment in off-lineoperation. The film has a width of preferably 0.5-5 m, more preferably0.7-3 m. When the film is once wound, the wound length is preferably300-30000 m, more preferably 500-10000 m, even more preferably 1000-7000m.

[Heat Treatment]

In the invention, in order to improve both of the optical property andthe dynamic property of matter, the formed cellulous acylate film issubjected to the heat treatment.

The method of the invention includes the processes of transporting thecellulous acylate film and performing the heat treatment in which thecellulous acylate film is maintained at (−285×S+1000)° C. or more andless than the melting point of the cellulose acylate film when it isassumed that the whole substitution degree is defined as S. Thetemperature of the heat treatment is more preferably in the range of(−285×S+1020)° C. to the melting point of the cellulose acylate film,further more preferably in the range of (−285×S+1040)° C. to (meltingpoint−5)° C., and the most preferably in the range of (−285×S+1050)° C.to (melting point−10)° C.

The cellulose acylate film of the invention can be preferably producedby a method comprising maintaining a cellulose acylate film at atemperature of Tc or higher and lower than the melting point of the filmfor a heat treatment. Tc represents a crystallization temperature (unit:° C.) of the cellulose acylate film before the heat treatment. Thetemperature of the heat treatment is preferably in the range of Tc to(melting point−5)° C., more preferably in the range of Tc to (meltingpoint−10)° C., still more preferably in the range of (Tc+5) to (meltingpoint−15)° C. Tc represents a crystallization temperature (unit: ° C.)of the cellulose acylate film before the heat treatment. Crystallizationtemperature is a temperature at which the cellulose acylate polymerarranges regularly to form a periodic structure. When the temperaturegoes over Tc, a structure observable in the X-ray diffraction grows. Themethod for measuring Tc is described below. Tc is generally higher thana glass transition temperature (Tg). For example, Tc of cellulosetriacetate film with a substitution degree of 2.92 is about 170° C. Themelting point mentioned above represents the melting point (unit: ° C.)of the cellulose acylate film before the heat treatment. The method formeasuring the melting point is described below. The melting point of acellulose triacetate film with a substitution degree of 2.85 is about285° C. and the melting point of cellulose triacetate film with asubstitution degree of 2.92 is about 290° C. These melting points varydepending on additives contained in the film and conditions in the filmpreparation.

In addition to the above control of the external force exerted on thecellulose acylate wave in the film-forming process, it is important thatthe heat treatment process includes a process of contracting the film inthe width direction for improving both of the optical property and thedynamic property of matter. The contracting process in the widthdirection may be included in the heat treatment process. In addition,the heat treatment process or the process before or after the heattreatment process may further include a process of extending the film inthe width direction. The contracting process in the width direction maybe performed to one end and the contracting process and the extendingprocess may be repeatedly performed.

The contraction ratio of the film is preferably in the range of 5% to80% before and after the process of contracting the film in the widthdirection, more preferably in the range of 10% to 70%, further morepreferably in the range of 20% to 60%, and the most preferably in therange of 25% to 50%. Since the heat treatment process including theprocess of contracting the film in the width direction is performed, thestructure observed with the X-ray diffraction can bidirectionally growin the in-plane direction. Accordingly, it is possible to obtain thelarge Re and to obtain the cellulous acylate film in which Rth as wellas Re is controlled. Even when a heat treatment not including thecontracting process in the width direction is performed and then thefilm is contracted in the width direction, this effect cannot beobtained as well.

When the end portion of the film is gripped by a tenter clip, thecontraction ratio in the width direction can be controlled with theratio of a broaden width of a rail. When the end portion of the film isnot fixed and is held by only a device fixing the film in the transportdirection such as a nip roll, the contraction ratio can be controlled byadjusting a distance between devices fixing the film in the transportdirection, adjusting a tension applied to the film, adjusting the amountof heat given to the film, or the like. The contraction ratio in thewidth direction was evaluated by measuring the whole width before andafter contracting the film.

Contraction Ratio in width direction (%)=100×(whole width beforecontraction−whole width after contraction)/whole width beforecontraction

In addition, by setting the temperature of the heat treatment asdescribed above, it is possible to manufacture the cellulous acylatefilm having the large Re of the invention. The heat treatment isgenerally performed for 0.01 minute or more and less than 60 minutes,preferably from 0.03 to 10 minutes, and more preferably from 0.05 to 5minutes.

[Stretching]

In order to adjust the value of Re and Rth, it is preferred that thecellulose acylate film being transported into a heat treatment zone issubjected to the heat treatment and the stretching at the same time, orthe cellulose acylate film may be subjected to the stretching afterbeing subjected to the heat treatment.

(Stretching Method)

For the stretching, longitudinal stretching may be carried out, forexample, in the apparatuses having a heating zone between two or moreapparatuses (for example, nip rolls, suction drum) which maintains thefilm in transport direction, in which the circumferential velocity on anexit side is larger, or stretching by grasping the both ends of the filmwith chucks for widening the film in the direction perpendicular to thetransport direction may be carried out. Otherwise, the above bothstretching method may be carried out in combination thereof.

In case that the cellulose acylate film is subjected to the stretchingafter being subjected to the heat treatment, first, the film may becooled after the heat treatment and then, preferably, subjected to thestretching process. In such a case, it is preferred that the film issubjected to the heat treatment by being transported to and then passedthrough the heat treatment zone; and the film is subjected to thestretching by grasping the both ends of the film with chucks forwidening the film in the direction perpendicular to the transportdirection.

The stretching ratio can be arbitrarily set in accordance with theretardation desired for the film, and is preferably in the range of 3 to500%, more preferably in the range of 5 to 100%, even more preferably inthe range of 10 to 80%, and especially preferably in the range of 20 to60%. The stretching may be effected in one step operation or multi-stepoperation. The ‘stretching ratio (%)’ herein means a value obtained byusing the following formula.

Stretching ratio (%)=100×{(length after stretching)−(length beforestretching)}/length before stretching

The stretching velocity in the stretching is preferably in the range of10 to 10000%/min, more preferably in the range of 20 to 1000%/min, andeven more preferably in the range of 30 to 800%/min.

The cellulose acylate film of the invention has preferably a monolayerstructure. A film having a monolayer structure is a polymer film of onesheet, instead of one composed of a plurality of stuck film materials.Also included is one sheet of polymer film produced from a plurality ofpolymer solutions by a sequential flow casting system or co-flow castingsystem. In this case, a polymer film having a distribution in thethickness direction can be obtained by suitably adjusting the type orblending amount of an additive, the molecular weight distribution of thepolymer, or the type of the polymer, etc. Also included is a film havingvarious functional portions such as an optical anisotropic portion, anantiglare portion, a gas barrier portion or a moisture resistant portionin one film.

[Surface Treatment]

The cellulose acylate film of the invention may be surface-treated inany desired manner to thereby improve its adhesiveness to variousfunctional layers (e.g., undercoat layer, back layer, opticallyanisotropic layer). The surface treatment includes glow dischargetreatment, UV irradiation treatment, corona treatment, flame treatment,saponification treatment (acid saponification treatment, alkalisaponification treatment). In particular, glow discharge treatment andalkali saponification treatment are preferred. The “glow dischargetreatment” as referred to herein is a plasma treatment of treating afilm surface in the presence of a plasma-exciting vapor. The details ofthe surface treatment are described in Hatsumei Kyokai DisclosureBulletin (No. 2001-1745, issued Mar. 15, 2001, Hatsumei Kyokai), and maybe conveniently referred to herein.

For improving the adhesiveness between the film surface of the celluloseacylate film of the invention and a functional layer to be formedthereon, an undercoat layer (adhesive layer) may be formed on the filmin place of or in addition to the surface treatment as above. Theundercoat layer is described in Hatsumei Kyokai Disclosure Bulletin (No.2001-1745, issued Mar. 15, 2001, Hatsumei Kyokai), page 32, which may beconveniently referred to herein. Functional layers that may be formed onthe cellulose acylate film of the invention are described in HatsumeiKyokai Disclosure Bulletin (No. 2001-1745, issued Mar. 15, 2001,Hatsumei Kyokai), pp. 32-45, which may be conveniently referred toherein.

<<Retardation Film>>

The cellulose acylate film of the invention may be used as a retardationfilm. “Retardation film” means an optical material that is generallyused in display devices such as liquid crystal display devices and hasoptical anisotropy, and its meaning may be the same as that of retarder,optical compensatory film, and optical compensatory sheet. In a liquidcrystal display device, the retardation film is used for the purpose ofincreasing the contrast of the display panel and improving the viewingangle characteristic and the coloration thereof.

Using the cellulose acylate film of the invention makes it easy toproduce a retardation film of which Re and Rth can be controlled in anydesired manner. For example, as a retardation film of which theretardation does not change dependently of the inclination angle to theslow axis direction, a film that satisfies Re≧50 nm and |Rth|≦15 nm canbe favorably produced; and a film that satisfies Re≧100 nm and |Rth|≦10nm can be produced more favorably.

The cellulose acylate film of the invention may be used as a retardationfilm directly as it is. Plural sheets of the cellulose acylate film ofthe invention may be laminated, or the cellulose acylate film ofinvention may be laminated with any other film not falling within thescope of the invention, and the resulting laminate films thus havingsuitably controlled Re and Rth may also be used as retardation films.For laminating the films, a paste or an adhesive may be used.

As the case may be, the cellulose acylate film of the invention may beused as a support of retardation films. An optically anisotropic layerof liquid crystal may be provided on the support to give a retardationfilm. The optical-anisotropic layer applicable to the retardation filmof the invention may be formed of, for example, a composition containinga liquid crystalline compound or a polymer film having birefringence.

The liquid crystalline compound is preferably a discotic liquidcrystalline compound or a rod-shaped liquid crystalline compound.

[Discotic Liquid Crystalline Compound]

Examples of the discotic liquid crystalline compound usable in theinvention are described in various publications (e.g., C. Destrade etal., Mol. Cryst. Liq. Cryst., Vol. 71, page 111 (1981); QuarterlyOutline of Chemistry, No. 22, Chemistry of Liquid Crystal, Chap. 5,Chap. 10, Sec. 2 (1994), by the Chemical Society of Japan; B. Kohne etal., Angew. Chem. Soc. Chem. Comm., page 1794 (1985); J. Zhang et al.,J. Am. Chem. Soc., Vol. 116, page 2655 (1994)).

Preferably, the discotic liquid crystalline molecules are fixed asaligned in the optically anisotropic layer; and most preferably, theyare fixed through polymerization. The polymerization of discotic liquidcrystalline molecules is described in JP-A-8-27284. For fixing discoticliquid crystalline molecules through polymerization, it is necessarythat a substituent of a polymerizing group is bonded to the disc core ofthe discotic liquid crystalline molecules. However, when a polymerizinggroup is directly bonded to the disc core, then the molecules couldhardly keep their alignment condition during the polymerization.Accordingly, a linking group is introduced between the disc core and thepolymerizing group. The discotic liquid crystalline molecules having apolymerizing group are disclosed in JP-A-2001-4387.

[Rod-Shaped Liquid Crystalline Compound]

Examples of the rod-shaped liquid crystalline compound usable in theinvention are azomethines, azoxy compounds, cyanobiphenyls, cyanophenylesters, benzoates, phenyl cyclohexanecarboxylates,cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines,alkoxy-substituted phenylpyrimidines, phenyldioxanes, tolans andalkenylcyclohexylbenzonitriles. However, not limited to suchlow-molecular rod-shaped liquid crystalline compounds, also usableherein are high-molecular rod-shaped liquid crystal compounds.

In the optically anisotropic layer, the rod-shaped liquid crystallinemolecules are preferably fixed as aligned therein; and most preferably,they are fixed through polymerization. Examples of the polymerizingrod-shaped liquid crystalline compound usable in the invention aredescribed, for example, in Macromol. Chem., Vol. 190, page 2255 (1989);Advanced materials, Vol. 5, page 107 (1993); U.S. Pat. No. 4,683,327,U.S. Pat. No. 5,622,648, U.S. Pat. No. 5,770,107; WO95/22586,WO95/24455, WO97/00600, WO98/23580, WO98/52905; JP-A-1-272551,JP-A-6-16616, JP-A-7-110469, JP-A-11-80081 and JP-A-2001-328973.

(Optically Anisotropic Layer of Polymer Film)

The optically anisotropic layer may be formed of a polymer film. Thepolymer film may be made of a polymer capable of expressing opticalanisotropy. Examples of the polymer capable of expressing opticalanisotropy are polyolefins (e.g., polyethylene, polypropylene,norbornenic polymer), polycarbonates, polyarylates, polysulfones,polyvinyl alcohols, polymethacrylates, polyacrylates, and celluloseesters (e.g., cellulose triacetate, cellulose diacetate). The polymermay be a copolymer or a polymer mixture of these polymers.

<<Polarizer>>

The cellulose acylate film or the retardation film of the invention maybe used as a protective film of a polarizer (polarizer of theinvention). The polarizer of the invention comprises a polarizing filmand two polarizer-protective films (cellulose acylate films) thatprotect both surfaces of the film, in which the cellulose acylate filmor the retardation film of the invention may be used as at least one ofthe polarizer-protective films.

In case where the cellulose acylate film of the invention is used as thepolarizer-protective film, then it is desirable that the celluloseacylate film of the invention is subjected to the above-mentionedsurface treatment (described also in JP-A-6-94915, JP-A-6-118232) forhydrophilication. For example, the film is preferably subjected to glowdischarge treatment, corona discharge treatment or alkali saponificationtreatment. In particular, when the polymer to constitute the celluloseacylate film of the invention is cellulose acylate, then the surfacetreatment is most preferably alkali saponification treatment.

For the polarizing film, for example, herein usable is a polyvinylalcohol film dipped and stretched in an iodine solution. In case wheresuch a polyvinyl alcohol dipped and stretched in an iodine solution isused as the polarizing film, then the treated surface of the celluloseacylate film of the invention may be directly stuck to both surfaces ofthe polarizing film with an adhesive. In the production method of theinvention, it is desirable that the cellulose acylate film is directlystuck to the polarizing film in that manner. The adhesive may be anaqueous solution of polyvinyl alcohol or polyvinyl acetal (e.g.,polyvinyl butyral), or a latex of vinylic polymer (e.g., polybutylacrylate). An especially preferred example of the adhesive is an aqueoussolution of completely-saponified polyvinyl alcohol.

In a liquid crystal display device, in general, a liquid crystal cell isprovided between two polarizers, and therefore, the device has fourpolarizer-protective films. The cellulose acylate film of the inventionmay be used as any of the four polarizer-protective films. Especiallyadvantageously in such a liquid crystal display device, the celluloseacylate film of the invention is used as the protective film to bedisposed between the polarizing film and the liquid crystal layer(liquid crystal cell). On the protective film to be disposed on theopposite side to the cellulose acylate film of the invention via thepolarizing film therebetween, optionally provided is a transparenthard-coat layer, an antiglare layer or an antireflection layer. Inparticular, the film of the invention is favorably used as thepolarizer-protective film on the outermost side of the display panel ofa liquid crystal display device.

<<Liquid Crystal Display Device>>

The transparent polymer film, the retardation film and the polarizer ofthe invention may be used in liquid crystal display devices of variousdisplay modes. Liquid crystal display modes to which the films areapplicable are described below. Of those modes, the transparent polymerfilm, the retardation film and the polarizer of the invention arefavorably used in liquid crystal display devices of VA mode and IPSmode. The liquid crystal display devices may be any of transmissiontype, reflection type or semi-transmission type.

(TN-Type Liquid Crystal Display Device)

The transparent polymer film of the invention may be used as a supportof the retardation film in a TN-type liquid crystal display devicehaving a TN-mode liquid crystal cell. TN-mode liquid crystal cells andTN-type liquid crystal display devices are well known from the past. Theretardation film to be used in TN-type liquid crystal display devices isdescribed in JP-A-3-9325, JP-A-6-148429, JP-A-8-50206, JP-A-9-26572; andMori et al's reports (Jpn. J. Appl. Phys., Vol. 36 (1997), p. 143; Jpn.J. Appl. Phys., Vol. 36 (1997), p. 1068).

(STN-Type Liquid Crystal Display Device)

The transparent polymer film of the invention may be used as a supportof the retardation film in an STN-type liquid crystal display devicehaving an STN-mode liquid crystal cell. In general, in an STN-typeliquid crystal display device, the rod-shaped liquid crystallinemolecules in the liquid crystal cell are twisted within a range of from90 to 360 degrees, and the product (Δnd) of the refractive anisotropy(Δn) of the rod-shaped liquid crystalline molecule and the cell gap (d)is within a range of from 300 to 1500 nm. The retardation film to beused in STN-type liquid crystal display devices is described inJP-A-2000-105316.

(VA-Type Liquid Crystal Display Device)

The transparent polymer film of the invention is especiallyadvantageously used as the retardation film or as a support of theretardation film in a VA-type liquid crystal display device having aVA-mode liquid crystal cell. The VA-type liquid crystal display devicemay be a multi-domain system, for example, as in JP-A-10-123576. Inthese embodiments, the polarizer that comprises the transparent polymerfilm of the invention contributes to enlarging the viewing angle of thedisplay panel and to improving the contrast thereof.

(IPS-Type Liquid Crystal Display Device and ECB-Type Liquid CrystalDisplay Device)

The transparent polymer film of the invention is especiallyadvantageously used as the retardation film, as a support of theretardation film or as a protective film of the polarizer in an IPS-typeliquid crystal display device and an ECB-type liquid crystal displaydevice having an IPS-mode or ECB-mode liquid crystal cell. In thedevices of these modes, the liquid crystal material is aligned nearly inparallel in black display, or that is, the liquid crystal molecules arealigned in parallel to the substrate face while no voltage is appliedthereto, thereby giving black display. In these embodiments, thepolarizer that comprises the transparent polymer film of the inventioncontributes to enlarging the viewing angle of the display panel and toimproving the contrast thereof.

(OCB-Type Liquid Crystal Display Device and HAN-Type Liquid CrystalDisplay Device)

The transparent polymer film of the invention is also especiallyadvantageously used as a support of the retardation film in an OCB-typeliquid crystal display device having an OCB-mode liquid crystal cell andin a HAN-type liquid crystal display device having a HAN-mode liquidcrystal cell. The retardation film to be used in an OCB-type liquidcrystal display device and a HAN-type liquid crystal display device ispreferably so designed that the direction in which the absolute value ofthe retardation of the film is the smallest does not exist both in thein-plane direction of the retardation film and in the normal directionthereof. The optical properties of the retardation film to be used in anOCB-type liquid crystal display device and a HAN-type liquid crystaldisplay device may vary depending on the optical properties of theoptically anisotropic layer therein, the optical properties of thesupport therein and the relative positioning of the opticallyanisotropic layer and the support therein. The retardation film to beused in an OCB-type liquid crystal display device and a HAN-type liquidcrystal display device is described in JP-A-9-197397. It is describedalso in a Mori et al's report (Jpn. J. Appl. Phys., Vol. 38 (1999), p.2837).

(Reflection-Type Liquid Crystal Display Device)

The transparent polymer film of the invention may be advantageously usedalso as the retardation film in TN-mode, STN-mode, HAN-mode and GH(guest-host)-mode reflection-type liquid crystal display devices. Thesedisplay modes are well known from the past. TN-mode reflection-typeliquid crystal display devices are described in JP-A-10-123478,WO98/48320, and Japanese Patent 3022477. The retardation film for use inreflection-type liquid crystal display devices is described inWO00/65384.

(Other Liquid Crystal Display Devices)

The transparent polymer film of the invention may be advantageously usedalso as a support of the retardation film in an ASM (axially symmetricaligned microcell)-type liquid crystal display device having an ASM-modeliquid crystal cell. The ASM-mode liquid crystal cell is characterizedin that the cell thickness is held by a position-adjustable resinspacer. The other properties of the cell are the same as those of theTN-mode liquid crystal cell. The ASM-mode liquid crystal cell and theASM-type liquid crystal display device are described in a Kume et al'sreport (Kume et al., SID 98 Digest 1089 (1988)).

(Hard Coat Film, Antiglare Film, Antireflection Film)

As the case may be, the transparent polymer film of the invention may beapplied to a hard coat film, an antiglare film and an antireflectionfilm. For the purpose of improving the visibility of flat panel displayssuch as LCD, PDP, CRT, EL, any or all of a hard coat layer, an antiglarelayer and an antireflection layer may be given to one or both surfacesof the transparent polymer film of the invention. Preferred embodimentsof such antiglare film and antireflection film are described in detailin Hatsumei Kyokai Disclosure Bulletin (No. 2001-1745, issued Mar. 15,2001, Hatsimei Kyokai), pp. 54-57, and are preferably employed also forthe transparent polymer film of the invention.

EXAMPLES Measuring Method

Hereinafter, methods of measuring and evaluating the characteristicsused in the following Examples and Comparative Examples will bedescribed.

[X-ray Diffractive Intensity]

Three points (the center portion of the film and end portions (positionsaway from both end portions by 5% of the whole width)) in the widthdirection of the film were sampled, the samples of 2 cm□ and 10 mm×1 mmwere taken, the average value of each point measured in accordance withthe above-mentioned method was calculated, and then a half-value widthof the peak and Ic/(Iam+Ic) at 2θ₂ were evaluated as observed in thesectional view in a direction parallel to the transport direction of thefilm. In addition, (Ic₁₁/Ic₁₂), (Ic₂₁/Ic₂₂), and (Ic₃₁/Ic₃₂) wereevaluated to calculate (Ic₁₁/Ic₁₂)/(Ic₃₁/Ic₃₂).

[Haze]

Five points (the center portion of the film, end portions (positionsaway from both end portions by 5% of the whole width)), and two pointsof middle portions between the center portion and the end portions) inthe width direction of the film were sampled and then the average valueof each point measured in accordance with the above-mentioned method wascalculated to evaluate the haze value.

[Sound-Wave Propagation Velocity]

Three points (the center portion of the film and end portions (positionsaway from both end portions by 5% of the whole width)) in the widthdirection of the film were sampled and then the average value of eachpoint measured in accordance with the above-mentioned method wascalculated to evaluate a direction in which the sound-wave propagationvelocity becomes the maximum.

[Retardation]

Five points (the center portion of the film, end portions (positionsaway from both end portions by 5% of the whole width)), and two pointsof middle portions between the center portion and the end portions) inthe width direction of the film were sampled each 100 m in thelongitudinal direction, the sample of 5 cm□ was taken, the average valueof each point measured in accordance with the above-mentioned method wascalculated to evaluate Re, Rth, and then the direction of the in-planeslow-phase axis. Further, the angle formed by the direction in which thesound-wave propagation velocity becomes the maximum and the direction ofthe slow-phase axis and the angle formed by the transport direction ofthe film and the direction (average value) of the slow-phase axis werecalculated.

[Tc]

20 mg of a sample was placed in a pan for the Differential ScanningCalorimetory (DSC) measurement and the temperature of the sample wasraised from 30° C. to 120° C. at a rate of 10° C./min in a nitrogenstream and kept at the temperature for 15 minutes, followed by coolingto 30° C. at a rate of −20° C./min. Thereafter, the temperature of thesample was raised again from 30° C. to 300° C. and the temperature atthe apex of an exothermal peak appeared during the temperature risingwas adopted as Tc.

[Melting Point]

20 mg of a sample was placed in a pan for the DSC measurement and thetemperature of the sample was raised from 30° C. to 120° C. at a rate of10° C./min in a nitrogen stream and kept at the temperature for 15minutes, followed by cooling to 30° C. at a rate of −20° C./min.Thereafter, the temperature of the sample was raised again from 30° C.to 300° C. and the temperature at the apex of an endothermal peakappeared during the temperature rising was adopted as a melting point ofthe film.

[Polarization Degree]

Two sheets of the polarizer produced herein were stuck together withtheir absorption axes kept in parallel to each other and thetransmittance (Tp) thereof was measured; and the two sheets were stucktogether with their absorption axes kept perpendicular to each other andthe transmittance (Tc) thereof was measured. The polarization degree (P)of the polarizer was calculated in accordance with the followingformula:

Polarization Degree P=((Tp−Tc)/(Tp+Tc))^(0.5)

Hereinafter, the characteristics of the invention will be moreconcretely described with reference to the following Examples andComparative Examples. In the following Examples, materials, the amountand the ratio thereof, details of the treatment, and the treatmentprocess may be suitably modified within the range of not impairing thepurpose of the invention. Accordingly, the invention should not belimitatively interpreted by the Examples mentioned below.

Examples 101 to 109, Comparative Examples 101 to 109 Preparation ofPolymer Solution 1) Cellulose Acylate

In respective Examples 101 to 109 and Comparative Examples 101 to 109,the cellulose acylates A or B described later was used according toTable 1. Each cellulose acylate was heated and dried at 120° C. to havea water content of 0.5% by mass or less. After that, 15 parts by mass ofcellulose acylate was used.

Cellulous Acylate A:

Powder of cellulous acetate having a substitution degree of 2.85 wasused. In cellulous acylate A, a viscosity-average polymerization degreewas 300, a substitution degree of 6-acetyl group was 0.89, a acetoneextraction was 7 mass %, a ratio of mass average molecular weight/numberaverage molecular weight was 2.3, a percentage of water content was 0.2mass %, a viscosity of 6 mass %-dichloromethane solvent was 305 mPa·s,residual acetic acid amount was 0.1 mass % or less, Ca-containing amountwas 65 ppm, Mg-containing amount was 26 ppm, Fe-containing amount was0.8 ppm, sulphuric acid ion-containing amount was 18 ppm, a yellow indexwas 1.9, and glass acetic acid amount was 47 ppm. An average particlesize was 1.5 mm and a standard deviation was 0.5 mm.

Cellulous Acylate B:

Powder of cellulous acetate having a substitution degree of 2.95 wasused. In cellulous acylate B, a viscosity-average polymerization degreewas 300 and a substitution degree of 6-acetyl group was 0.94.

[Substitution Degree]

The substitution degree of acyl of cellulose acylate was determined bythe use of ¹³C-NMR according to the method described in Carbohydr. Res.273 (1995), pp. 83 to 91 (by Tezuka, et al).

[Polymerization Degree]

The cellulose acylate produced herein is absolutely dried, then about0.2 g thereof is accurately weighed, and dissolved in 100 mL of a mixedsolvent of dichloromethane:ethanol=9:1 (mass ratio). Using an Ostwaldviscometer, the time (second) taken by its dropping at 25° C. ismeasured, and the polymerization degree DP is calculated according tothe following formulae.

η_(rel) =T/T ₀

[η]=ln(η_(rel))/C

DP=[η]/Km

wherein T indicates the time (second) taken by the dropping sample; T₀indicates the time (second) taken by the dropping solvent alone; inindicates a natural logarithm; C indicates the concentration (g/L); andKm is 6×10⁻⁴.

2) Solvent

In respective Examples and Comparative Examples, either the followingsolvent A was used according to Table 1. Each solvent had the watercontent of 0.2% by mass or below.

Solvent A:

A mixed solvent in which dichloromethane/methanol/butanol (83/15/2 partsby mass) are mixed was used.

3) Additive

In respective Examples and Comparative Examples, either an additive A orB having the following composition was used according to Table 1.

Additive A:

Triphenyl phosphate (1.2 parts by mass)

Biphenyldiphenyl phosphate (0.6 part by mass)

Silicon dioxide fine particles (particle size: 20 nm, Mohs hardness:about 7) (0.08 part by mass)

Additive B:

Silicon dioxide fine particles (particle size: 20 nm, Mohs hardness:about 7) (0.08 part by mass)

4) Dissolution

In respective Examples and Comparative Examples, the dissolution processA or B described later was used according to Table 1.

Dissolution Process A:

The solvent and the additive mentioned above were put into a 400-literstainless dissolution tank, which has stirring blades and is cooled withcooling water that runs around its periphery. With stirring anddispersing them therein, the cellulose acylate was gradually added tothe tank. After the addition, this was stirred at room temperature for 2hours. After thus swollen for 3 hours, this was again stirred to obtaina cellulose acylate solution.

For the stirring, used were a dissolver-type eccentric stirring shaftthat runs at a peripheral speed of 15 m/sec (shear stress, 5×10⁴kgf/m/sec² [4.9×10⁵ N/m/sec²]) and a stirring shaft that has an anchorblade at the center axis thereof and runs at a peripheral speed of 1m/sec (shear stress, 1×10⁴ kgf/m/sec² [9.8×10⁴ N/m/sec²]). For theswelling, the high-speed stirring shaft was stopped and the peripheralspeed of the anchor blade-having stirring shaft was reduced to 0.5m/sec.

The swollen solution in the tank was heated up to 50° C. via a jacketedpipe line, and then further heated up to 90° C. under a pressure of 2MPa for complete dissolution. The heating time was 15 minutes. In thisstage, the filter, the housing and the pipe line that are exposed tohigh temperature are all made of Hastelloy alloy having good corrosionresistance; and the system is covered with a jacket for circulating aheat carrier therethrough for keeping the system warmed and heated.

Next, this was cooled to 36° C. to obtain a cellulose acylate solution.

Dissolution Process B:

The solvent and the additive mentioned above were put into a 400-literstainless dissolution tank, which has stirring blades and is cooled withcooling water that runs around its periphery. With stirring anddispersing them therein, the cellulose acylate was gradually added tothe tank. After the addition, this was stirred at room temperature for 2hours. After thus swollen for 3 hours, this was again stirred to obtaina cellulose acylate solution.

For the stirring, used were a dissolver-type eccentric stirring shaftthat runs at a peripheral speed of 15 m/sec (shear stress, 5×10⁴kgf/m/sec² [4.9×10⁵ N/m/sec²]) and a stirring shaft that has an anchorblade at the center axis thereof and runs at a peripheral speed of 1m/sec (shear stress, 1×10⁴ kgf/m/sec² [9.8×10⁴ N/m/sec²]). For theswelling, the high-speed stirring shaft was stopped and the peripheralspeed of the anchor blade-having stirring shaft was reduced to 0.5m/sec.

The swollen mixture in the tank was transported via a screw pump ofwhich center part of the shaft was heated at 30° C., and passed througha cooling part, which was cooled from the periphery part of the screw,at −70° C. for 3 min. The cooling process was carried out by usingrefrigerant of −75° C. cooled in a refrigerator. The mixture obtained bythe cooling process was transported to the stainless vessel via thescrew pump of which column was heated at 30° C.

Next, this was stirred at 30° C. for 2 hours to obtain a celluloseacylate solution.

5) Filtration

The cellulose acylate solution thus obtained was filtered through apaper filter sheet (#63, manufactured by Toyo Roshi Kaisha, Ltd.) havingan absolute filtration accuracy of 10 μm, and then through a sinteredmetal filter sheet (FH025, manufactured by Pall Corporation) having anabsolute filtration accuracy of 2.5 μm to obtain a polymer solution.

(Production of Film)

In respective Examples and Comparative Examples, any one of film-formingprocess A to C described later was used according to Table 1.

Film-Forming Process A:

The cellulose acylate solution was heated at 30° C., passed through acaster, Giesser, and cast onto a mirror-faced stainless support having adrum shape one of 3 m diameter and the surface temperature of thesupport was set at −5° C. The casting width was 200 cm. The spacetemperature in the entire casting zone was set at 15° C. At 50 cm beforethe end point of the casting zone, the cellulose acylate film thus castand rolled was peeled off from the band and then the both ends of thefilm was clipped with pintenters. The amount of a residual solvent, thespeed for the support of peeling off (peeling off roll draw), and thesurface temperature of the film at the instant of peeling off were shownin Table 1. The cellulose acylate web held with pintenters was exposedto drying air applied thereto at 45° C. Next, this was dried at 110° C.for 5 minutes and then at 140° C. for 10 minutes to obtain a transparentfilm of cellulose acylate having a thickness of 80 μm.

Film-Forming Process B:

The above solution of cellulose acylate film was heated at 30° C.,passed through a caster, Giesser, and cast onto a mirror-faced stainlesssupport which is a drum having a diameter of 3 m. The temperature of thesurface of the support was set at −5° C., and the casting width was 200cm. The space temperature in the entire casting zone was set at 15° C.At 50 cm before the end point of the casting zone, the cellulose acylatefilm thus cast and rolled was peeled off from the drum, and then theboth ends of the film was clipped with pin tenters. The amount of aresidual solvent, the speed for the support of peeling off (peeling offroll draw), and the surface temperature of the film at the instant ofpeeling off were shown in Table 1. The cellulose acylate film held withpin tenters was transported to a drying zone. At first, the film wasexposed to drying air applied thereto at 45° C. Next, this was dried at110° C. for 5 minutes and then at 140° C. for 10 minutes to obtain atransparent film of cellulose acylate having a thickness of 80 μm.

Film-Forming Process C:

A film-forming process was performed according to the film-formingprocess A, wherein the surface temperature of the support was set at 0°C. and the space temperature in the entire casting zone was set at 45°C.

(Heat Treatment)

In respective Examples and Comparative Examples, the heat treatingmethod used was selected from following heat treating method A to C andwas shown in Table 1.

The elongation of the film was obtained according to the followingformula in such a manner that gauge lines were given to the film at aconstant interval in the direction perpendicular to the transportdirection of the film and the interval was measured before and after theheat treatment.

Elongation of film (%)=100×{(interval of gauge lines after heattreatment)−(interval of gauge lines before heat treatment)}/interval ofgauge lines before heat treatment

Heat Treatment Process A

A heat treatment was subjected to the obtained film by using a devicehaving a heating zone between two nip rolls. A contraction ratio in thewidth direction was controlled by adjusting the temperature of theheating zone and the circumferential velocity of the nip rolls. Alongitudinal/transverse ratio (distance between nip rolls/base width)was adjusted to be 3.3, the base temperature before the film enters theheating zone was set to 25° C., and the film was heated in the heatingzone at the temperature described in Table 1 for one minute.

Heat Treatment Process B

While the obtained film was gripped by tenter clips, the film wassubjected to the heat treatment by using a device which allows the filmto pass through the heating zone. A contraction ratio in the widthdirection was controlled by adjusting a width of a rail. The basetemperature before the film enters the heating zone was set to 25° C.and the film was heated in the heating zone at the temperature describedin Table 1 for one minute.

Heat Treatment Process C

Heat Treatment Process C was performed in the same manner as HeatTreatment Process B other than the heating time of 60 minutes differentfrom the heating time of Heat Treatment Process B.

(Evaluation of Transparent Polymer Film)

The respective transparent polymer films thus obtained were evaluated.The results are shown in Table 1 below.

The slow phase axis of Re of the film was observed in the widthdirection in Examples, and observed in the transport direction of thefilm in Comparative Examples. The variation (variation of valuesmeasured at five portions) of Re and Rth evaluated based on theabove-mentioned method was at most ±1 nm and at most ±2 nm,respectively, for all the samples. The fluctuation range in thedirection of the slow phase axis was below 1°.

TABLE 1 Heat Film Forming Process Treat- Cellu- (Supporter- Heat mentCon- Film lous Disso- Volatil- Exten- Web Temper- (285 × Melting Treat-Temper- traction Exten- Acylate Addi- lution ization sion ature) S +Point Tc ment ature Ratio sion Type tive Process Type [%] [%] [° C.]1000) [° C.] [° C.] Process [° C.] [%] [%] Example 101 A A A A 270 20 3188 285 185 A 200 32 25 Example 102 A A A A 270 20 3 188 285 185 A 24035 24 Example 103 A A A A 270 20 3 168 285 185 A 260 44 40 Example 104 AB A A 270 20 2 188 290 190 A 240 41 51 Example 105 A A A A 100 20 3 188285 190 A 240 33 25 Example 106 A A A A 370 20 4 188 285 185 A 240 30 24Example 107 A A A A 270 50 3 188 285 180 A 240 35 28 Example 108 A A A A270 100 3 188 285 180 A 240 37 33 Example 109 B A B A 270 20 3 159 285150 A 240 43 42 Comparative A A A A 270 20 3 188 285 185 A 160 7 10Example 101 Comparative A A A A 270 20 3 188 285 185 A 180 29 20 Example102 Comparative A A A A 270 20 3 188 285 185 A 300 — — Example 103Comparative A A A B 50 1 5 188 285 185 A 240 37 60 Example 104Comparative A A A A 100 5 2 188 285 185 A 240 35 23 Example 105Comparative A A A C 40 10 −5 188 285 190 B 200 3 2 Example 106Comparative A A A A 270 20 5 188 285 185 C 260 3 2 Example 107Comparative A A A A 270 20 3 188 285 185 None — — — Example 108Comparative A A A B 50 5 6 188 285 185 None — — — Example 109 X-rayDiffractive Intensity Re Rth Slow-Phase Axis Angle Ic_(i)/ Half ValueIc/ (Ic₁₁/Ic₁₂)/ 2θ4 Half Value Haze Average Average |Rth|/Re SoundTransport IC_(o) Width [°] (Iam + Ic) (IC₃₁/IC₃₂) [°] Width [°] [%] [nm][nm] Average Velocity [°] Direction [°] Example 101 0.38 2.8 0.47 0.5513.3 1.8 0.2 28 26 0.9 90 90 Example 102 0.36 1.3 0.68 0.41 10.6 1.3 0.2186 3 0.0 90 90 Example 103 0.21 0.4 0.80 0.36 10.4 0.4 0.2 224 1 0.0 9090 Example 104 0.35 1.2 0.73 0.40 10.5 1.2 0.2 193 1 0.0 90 90 Example105 0.38 1.3 0.67 0.43 10.5 1.3 0.2 191 9 0.1 90 90 Example 106 0.34 1.30.67 0.40 10.5 1.3 0.2 178 2 0.0 90 90 Example 107 0.31 1.3 0.69 0.4010.5 1.3 0.2 203 10 0.1 90 90 Example 108 0.28 1.3 0.69 0.39 10.5 1.30.2 224 15 0.1 90 90 Example 109 0.25 1.2 0.76 0.39 10.4 1.2 0.2 248 90.0 90 90 Comparative 0.43 3.2 0.40 0.55 — — 0.4 22 37 1.7 0 0 Example101 Comparative 0.41 3.0 0.42 1.47 — — 0.3 12 34 2.8 0 0 Example 102Comparative — — — — — — — — — — — — Example 103 Comparative 0.93 1.30.62 1.52 10.5 1.3 0.2 163 −94 0.6 90 90 Example 104 Comparative 0.731.4 0.66 1.14 10.5 1.4 0.2 161 −85 0.5 90 90 Example 105 Comparative0.41 3.0 0.44 0.63 — — 1.3 11 12 1.1 90 90 Example 106 Comparative 0.433.4 0.90 0.74 10.3 1.6 3.9 11 13 1.2 90 90 Example 107 Comparative 0.393.1 0.42 0.63 — — 0.2 5 42 8.4 90 90 Example 108 Comparative 0.56 3.70.38 0.56 — — 0.3 1 49 49.0 90 90 Example 109

As shown in Table 1, by performing the heat treatment in accordance withthe method of the invention, it is possible to manufacture a cellulousacylate film having a preferable X-ray diffractive intensity, having thelow haze, improving both of an optical property and a dynamic propertyof matter, and controlling a balance between Re and Rth of the film.However, when the condition of the heat treatment does not fall withinthe range of the invention, it is difficult to manufacture the cellulousacylate film having a preferable X-ray diffractive intensity and thedirection of the slow phase axis is not preferable. Further, inComparative Example 103, the film was molten and cut off in the courseof transporting the film.

Example 151 Re-Extension of Film

Both ends of the cellulous acylate film of Example 108 completing theheat treatment were gripped tenter clips and then the film was extendedin the heating zone at 200° C. in a direction perpendicular to thetransport direction by 30%. In the obtained cellulous acylate film,Ic_(i)/Ic_(o) was 0.27, a half-value width was 1.4°, Ic/(Iam+Ic) was0.67, (Ic₁₁/Ic₁₂)/(Ic₃₁/Ic₃₂) was 0.38, haze was 0.2%, Re was 216 nm,Rth was 42 nm, |Rth|/Re was 5.1, an angle formed by a direction of aslow-phase axis and a direction in which a sound velocity becomes themaximum was 90°, and an angle formed by a direction of a slow-phase axisand the transport direction of the film was 90°. The extension ratio wasobtained by drawing gauge lines at regular intervals in a directionparallel to the transport direction of the film and then measuring thegauge lines before and after the extension.

Extension Ratio(%)=100×(interval of gauge line after extension−intervalof gauge line before extension)/(interval of gauge line beforeextension)

Comparative Example 110

A bi-refractive film was obtained by using the cellulous acylate film ofComparative Example 106 in accordance with Example 5 of JP-A-5-157911.The angle formed by a direction of the in-plane slow-phase axis of thefilm and a direction in which the sound velocity becomes the maximum orthe transport direction was 3°. Accordingly, the angle was notpreferable. The range of fluctuation in the direction of the slow-phaseaxis was 8°, which was large. Further, in the non-uniformities(non-uniformities of measured value of five points) of Re and Rth, Reand Rth were ±25 nm and ±43 nm, which were large.

Comparative Example 111

A bi-refractive film was obtained in accordance with Example 1 ofJP-A-2006-28346. The angle formed by a direction of the in-planeslow-phase axis and a direction in which the sound velocity becomes themaximum was 0°.

Example 201 Manufacture of Laminating Retardation Film

The cellulous acylate film of the invention may be used as a retardationfilm itself. However, herein, by adhering the film using an adhesive inthe roll-to-roll manner, the retardation film which controlled Rth/Reratio was manufactured.

Fujitac TD80UL (manufactured by Fuji Photo Film Co., Ltd.) and the filmof Example 151 were adhered to each other by using an adhesive. Then, Reand Rth were measured in the above-described method. The result was thatRe was 213 nm and Rth was 86 nm. In addition, the angle formed by adirection of the in-plane slow-phase axis of the retardation film andthe transport direction was 90°.

Examples 301 to 311, Comparative Examples 301 to 310 Manufacture ofPolarizer

The obtained film was subjected to saponification treatment, therebymanufacturing a polarizer.

1) Saponification of Film

A film A and film B shown in Table 2 below were dipped in a 1.5 mol/L ofNaOH aqueous solution (saponification solution) that wastemperature-controlled at 55° C. for 2 minutes and then washed withwater. After that, the films were dipped in a 0.05 mol/L sulfuric acidaqueous solution for 30 seconds and further passed through a waterwashing bath. Then, the films were subjected to air knife treatmentthree times to remove water and retained in a drying zone at 70° C. for15 seconds to be dried, thereby manufacturing saponified films.

2) Manufacture of Polarizing Layer

According to Example 1 described in JP-A-2001-141926, the film wasstretched in a longitudinal direction by giving difference incircumferential velocities to two pairs of nip rolls, thereby preparinga polarizing layer having a thickness of 20 μm.

3) Sticking

The polarizing layer thus obtained and the two films (film A and film Brespectively, whose combination in respective Examples and ComparativeExamples is shown in Table 2 below) selected from the saponified filmswere disposed so that the saponified surfaces of the film faced to thepolarizing film and sandwiched the polarizing layer, and then stuck toeach other by the use of a 3% PVA (PVA-117H, manufactured by KURARAYCo., Ltd.) aqueous solution as an adhesive in such a manner that thepolarizing axis crossed perpendicularly to the longitudinal direction ofthe film using roll-to-roll process.

In Table 2, ‘TAC B’ indicates FUJITAC TD80UF (manufactured by Fujifilmcorporation; moisture permeability=430 g/(m²·day) at 40° C. and arelative humidity of 90%) (80 μm in terms of thickness), ‘polycarbonate’indicates Panlite C1400 (manufactured by TEIJIN CHEMICALS, Ltd.;moisture permeability=30 g/(m²·day) at 40° C. and a relative humidity of90%) (80 μm in terms of thickness), ‘COP1’ indicates ARTON FILM(thickness: 80 μm, manufactured by JSR corporation; moisturepermeability=30 g/(m²·day) at 40° C. and a relative humidity of 90%) (80μm in terms of thickness), and ‘COP2’ indicates ZEONOR FILM (thickness:100 μm, manufactured by ZEON; moisture permeability=0 g/(m²·day) at 40°C. and a relative humidity of 90%) (80 μm in terms of thickness).

In Comparative Example 304, the sticking was carried out by using a filmwhich had been subjected to surface treatment replaced by coronatreatment.

In Comparative Example 104, the sticking was not carried out as thecracking of the film was occurred at the sticking.

(Evaluation of Polarizer) [Initial Polarization Degree]

The polarization degree of the polarizer was calculated according to themethod described above. The result is shown in Table 2.

[After Storage Polarization Degree 1]

The film A side of the polarizer was stuck to a glass plate with anadhesive, and was left under conditions of 60° C. and a relativehumidity of 95% for 500 hours and the polarization degree after thelapse of time (after storage polarization degree) was calculatedaccording to the aforementioned method. The results are shown in Table 2below.

[After Storage Polarization Degree 2]

The film A side of the polarizer was stuck to a glass plate with anadhesive, and was left under conditions of 90° C. and a relativehumidity of 0% for 500 hours and the polarization degree after the lapseof time (after storage polarization degree) was calculated according tothe aforementioned method. The results are shown in Table 2 below.

TABLE 2 Initial After Storage After Storage Polarization PolarizationPolarization Degree Degree 1 Degree 2 Film A Film B [%] [%] [%] Example301 Example 101 TAC A 99.9 99.9 99.9 Example 302 Example 102 TAC A 99.999.9 99.9 Example 303 Example 103 TAC A 99.9 99.9 99.9 Example 304Example 104 TAC A 99.9 99.9 99.9 Example 305 Example 105 TAC A 99.9 99.999.9 Example 306 Example 106 TAC A 99.9 99.9 99.9 Example 307 Example107 TAC A 99.9 99.9 99.9 Example 308 Example 108 TAC A 99.9 99.9 99.9Example 309 Example 109 TAC A 99.9 99.9 99.9 Example 310 Example 151 TACA 99.9 99.9 99.9 Example 311 Example 151 Example 151 99.9 99.9 99.9Comparative Example 301 Polycarbonate Polycarbonate (Unmeasurable due toinsufficient sticking property) Comparative Example 302 COP1 COP1(Unmeasurable due to insufficient sticking property) Comparative Example303 COP2 COP2 (Unmeasurable due to insufficient sticking property)Comparative Example 304 COP2 COP2 99.9 99.9 (Bubble generation)Comparative Example 305 Comparative Example 101 TAC A 99.9 99.9 99.9Comparative Example 306 Comparative Example 102 TAC A 99.9 99.9 99.9Comparative Example 307 Comparative Example 104 TAC A 99.9 99.9 99.9Comparative Example 308 Comparative Example 105 TAC A 99,9 99.9 99.9Comparative Example 309 Comparative Example 106 TAC A 99.9 99.9 99.9Comparative Example 310 TAC A TAC A 99.9 99.9 99.9

[Polarization Degree 3 with lapse of time]

The film A of the polarizing plate was adhered to the glass plate andwas kept under the condition where the temperature is 60° C. and therelative humidity is 95% for 50 hours and the condition where thetemperature is 90° C. and the relative humidity is 0% for 50 hours to besubjected to tests for 10 cycles. Then, the polarization degree wasmeasured. As shown in Example 301 to 311, the result was that the samplein which an extending direction of the polarizer and a direction thesound-wave propagation velocity becomes the maximum are parallel to eachother did not vary after lapse of time.

(Mounting Assessment onto IPS Liquid Crystal Display Device)

When the polarizing plates of Example 302 and Example 304 were mountedon IPS Liquid Crystal display device (32V High-Vision Liquid CrystalTelevision Monitor (W32-L7000), manufactured by Hitachi, Ltd.) insteadof a polarizing plate mounted in advance, the property of viewing anglewas improved. The improvement effect of the viewing angle property wasbetter than that of Example 301. The reason was considered because theapplication of the retardation film in which the balance of Re and Rthis enough controlled resulted in the compensation of thethree-dimensionally sufficient viewing angle. On the contrary, when thepolarizing plates of Comparative Examples 305 to 310 were mountedthereon, the viewing angle property was not improved. Even when theviewing angle property was improved, the improvement was not sufficient.

(Mounting Assessment 2 onto IPS Liquid Crystal Display Device)

Two sets of Polarizing plates of Example 310 were arranged and then theliquid crystal display device was manufactured. In the liquid crystaldisplay device, Example 310, IPS liquid crystal cell, and Example 310were piled in this order, such that the film A could be configured asthe liquid crystal cell side. At this time, the transmission axes of theupper and lower polarizing plates were allowed to be perpendicular toeach other and the transmission axis of the upper polarizing plate wasallowed to be parallel to the molecular longitudinal axis (that is, theslow-phase axis of the optical compensation layer is perpendicular tothe molecular longitudinal axis of the liquid crystal cell). The liquidcell or electrode board is IPS. The known things were used as the liquidcell or electrode board. The alignment of the liquid crystal cell is ahorizontal alignment and the liquid crystal has positive permittivityanisotropy. The liquid crystal improved for IPS liquid crystal andplaced on the market was used. The matter property of the liquid crystalcell was as follows: Δn of liquid crystal: 0.099, cell gap of liquidcrystal layer: 3.0 μm, pretilt angle: 5°, and rubbing directions ofupper and lower boards: 75°. The liquid crystal display devicemanufactured in this manner had the excellent viewing angle property. Onthe contrary, when the polarizing plate of Comparative Example 308 wasused, the viewing angle property was degraded.

INDUSTRIAL APPLICABILITY OF THE INVENTION

According to the invention, it is possible to provide a cellulousacylate film in which both of the optical property and the matterproperty are improved. In addition, it is possible to provide acellulous acylate film satisfying the above-mentioned condition,controlling the balance of the Re and Rth of the film, and being usefulas a retardation film. Since the cellulous acylate film has propermoisture permeability, the film can be adhered to the polarizing film online. Accordingly, the polarizing plate having excellent visibility andhigh productivity can be provided. In addition, the liquid crystaldisplay having high-reliability can be provided. Consequently, theinvention has high applicability.

While the present invention has been described in detail and withreference to specific embodiments thereof, it will be apparent to oneskilled in the art that various changes and modifications can be madetherein without departing from the spirit and scope thereof.

The present disclosure relates to the subject matter contained inJapanese Patent Application No. 139568/2006 filed on May 18, 2006 andJapanese Patent Application No. 132399/2007 filed on May 18, 2007, whichare expressly incorporated herein by reference in their entirety. Allthe publications referred to in the present specification are alsoexpressly incorporated herein by reference in their entirety.

The foregoing description of preferred embodiments of the invention hasbeen presented for purposes of illustration and description, and is notintended to be exhaustive or to limit the invention to the precise formdisclosed. The description was selected to best explain the principlesof the invention and their practical application to enable othersskilled in the art to best utilize the invention in various embodimentsand various modifications as are suited to the particular usecontemplated. It is intended that the scope of the invention not belimited by the specification, but be defined claims set forth below.

1. A cellulous acylate film in which X-ray diffractive intensitysatisfies the Formula (I) below and in which a half-value width of thepeak at 2θ₂ is 2.8° or less as observed in the sectional view in adirection parallel to the transport direction of the film:0.00≦Ic _(i) /Ic _(o)<0.60;  Formula (I) wherein Ic_(i) and Ic_(o) arerepresented by the following Formula (IV) and (V) respectively:Ic _(i) =Ic ₁₁ /Ic ₁₂;  Formula (IV)Ic _(o)={(Ic ₂₁ /Ic ₂₂)+(Ic ₃₁ /Ic ₃₂)}/2;  Formula (V) wherein Ic₁₁ toIc₃₂ are obtained by the Formulae (II) and (III) below, Ic₁₁ and Ic₁₂indicate Ic in a direction in which I₂ becomes the maximum in adiffraction picture observed in a direction perpendicular to the surfaceof the film and Ic in a direction perpendicular thereto respectively,Ic₂₁ and Ic₂₂ indicate Ic in a direction in which I₂ becomes the maximumin a diffraction picture observed in the sectional view in a directionparallel to the transport direction of the film and Ic in a directionperpendicular thereto respectively, and Ic₃₁ and Ic₃₂ indicate Ic in adirection in which I₂ becomes the maximum in a diffraction pictureobserved in the sectional view in a direction perpendicular to thetransport direction of the film and Ic in a direction perpendicularthereto respectively:Iam=I ₁+{(I ₃ −I ₁)/(2θ₃−2θ₁)}×(2θ₂−2θ₁);  Formula (II)Ic=I ₂ −Iam;  Formula (III) wherein when it is assumed that θ is theBragg angle, 2θ₁ indicates 2θ at which the intensity becomes the minimumin the 2θ range of 4° to 5°, 2θ₂ indicates 2θ at which the intensitybecomes the maximum in the 2θ range of 5° to 10°, 2θ₃ indicates 2θ atwhich the intensity becomes the minimum in the 2θ range of 14° to 16°,I₁ indicates a diffractive intensity at 2θ₁, I₂ indicates a diffractiveintensity at 2θ₂, I₃ indicates a diffractive intensity at 2θ₃.
 2. Thecellulous acylate film according to claim 1, wherein the diffractivepicture observed in the sectional view in a direction parallel to thetransport direction of the film has at least one peak in the 2θ rangebetween 2θ₂ and 2θ₃, the maximum peak in the 2θ range between 2θ₂ and2θ₃ exists at 2θ₄ in the 2θ range of 10° to 12.5°, and a half-valuewidth of the peak at 2θ₄ is less than 2°.
 3. The cellulous acylate filmaccording to claim 1, wherein the X-ray diffractive intensity observedin the sectional view in a direction parallel to the transport directionof the film satisfies the following Formula (VI):0.40≦Ic/(Iam+Ic)≦0.85.  Formula (VI)
 4. The cellulous acylate filmaccording to claim 1, wherein the haze is 3% or less.
 5. The cellulousacylate film according to claim 1, wherein the in-plane retardation isin the range of 5 to 600 nm and the retardation in the thicknessdirection is more than 0 nm.
 6. The cellulous acylate film according toclaim 1, wherein an angle formed by a direction of an in-planeslow-phase axis and a direction in which a sound-wave propagationvelocity becomes the maximum is in the range of 75° to 105°.
 7. A methodof manufacturing a cellulous acylate film, the method comprising:extending a cellulous acylate web by 15% to 300% in a transportdirection in the state where an amount of a residual solvent is in therange of 5% to 1000% by mass; and performing a heat treatment at thetemperature of (−285×S+1000)° C. or more and less than the melting pointof a cellulous acylate film for 0.01 minute or more and less than 60minutes, wherein the step of performing the heat treatment includescontracting the film in the width direction of the film and S indicatesa total substitution degree of the cellulous acylate film.
 8. A methodof manufacturing a cellulous acylate film, the method comprising:extending a cellulous acylate web by 15% to 300% in a transportdirection in the state where an amount of a residual solvent is in therange of 5% to 1000% by mass; and performing a heat treatment at thetemperature of Tc or more and less than the melting point of a cellulousacylate film for 0.01 minute or more and less than 60 minutes, whereinthe step of performing the heat treatment includes contracting the filmin the width direction of the film, Tc indicates a crystallizationtemperature (unit: ° C.) of the cellulose acylate film before the heattreatment and S indicates a total substitution degree of the cellulousacylate film.
 9. The method of manufacturing a cellulous acylate filmaccording to claim 7, wherein the cellulous acylate web extends underthe condition that the temperature of the web is in the range of(Ts−100) to (Ts−0.1)° C. and Ts indicates a surface temperature of aflexible supporter.
 10. A cellulous acylate film manufactured by themethod according to claim
 7. 11. The cellulous acylate film according toclaim 1, wherein an angle formed by a direction of in-plane slow-phaseaxis of the film and a transport direction is in the range of 80° to100°.
 12. A retardation film having at least one sheet of cellulousacylate film according to claim
 1. 13. A polarizing plate having atleast one sheet of cellulous acylate film according to claim
 1. 14. Thepolarizing plate according to claim 13, wherein the cellulous acylatefilm is directly adhered to a polarizing film.
 15. A liquid crystaldisplay device comprising at least one sheet of the cellulous acylatefilm according to claim
 1. 16. The method of manufacturing a cellulousacylate film according to claim 8, wherein the cellulous acylate webextends under the condition that the temperature of the web is in therange of (Ts−100) to (Ts−0.1)° C. and Ts indicates a surface temperatureof a flexible supporter.
 17. A cellulous acylate film manufactured bythe method according to claim 8.